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Vol.5, No.1 – November 2014

Activity modeling for energy-efficient design of new hospitals

 

SUMMARY

Background: Buildings in Europe counts for 40% of primary energy consumption. Among different building categories like offices, dwellings and so on, hospitals are one of the two most energy-intensive. This article reports some of the results from the “Low Energy Hospitals” project supported by the Norwegian Research Council (NRC) and the participating companies. The aim is to show how energy use in hospitals could be reduced by 50 %. Many projects are running in Norway and the rest of the world aimed at improving energy performance in buildings. This project focusses on hospitals in particular. The main thesis is that if the diversity of functional areas within a hospital is better understood by the design team, and if energy becomes an integrated part of the early planning of hospitals, then a halving of consumption is attainable by delivering and recycling energy according to the changing activity levels in each area.

Method: The data was collected from three hospitals in the South-East hospital region of Norway, giving actual data on energy use, occupancy, and clinical activities on an hourly basis. These data were used to make an activity profile, telling which activity is occurring in different parts of the hospitals. Patient register data was used together with interviews to find out when personnel were present. Design data for hospital technical systems in the various areas was also collected. Norwegian hospitals categorize their area into specific functional areas, such as bed wards, offices, operating theatres and so forth; this was used by the project to characterize energy performance.

Result: The activity data clearly show that hospitals are not operated 24 hours 7 days a week; only a small percentage of floor area is used around the clock, and more than half of hospital area follows normal office hours. Even during active hours the simultaneous occupancy level was relatively low. This activity demand was not reflected in the energy data, which showed a large and continuous base-load for electrical and ventilation energy. A review of the design data confirmed how hospitals differ from all other building categories: (1) larger internal

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loads from hospital-specific equipment using high-value electricity, whose waste heat also demands cooling energy (2) large ventilation demand coupled with lower rate of heat recovery due to unnecessarily strict hygiene requirements.

Conclusion: Hospital equipment and ventilation designs did not allow energy supply to follow the actual demand from activity, and that the reduction potential is about 50%. We propose activity modeling as an integrated design method to evaluate new designs for demand-control of hospital equipment and ventilation energy.  

1. Introduction 

1.1 Hospital design needs a new approach to energy efficiency! 

Faced with the risks of climate change, the world must now cut carbon emissions. The developed world must reduce its energy demand and developing economies must find a way to avoid the path to an energy-intensive society. Buildings, and especially hospitals, have the greatest potential for reducing energy consumption.

Buildings typically account for about 40% of energy production, and hospital buildings are particularly energy-intensive. Figure 1 (Statistics Norway, Report 2011/17) shows that hospitals are the most energy-intensive of types directly operated by the public sector.

Figure 1 Energy intensity for buildings in services industries, Norway 2008, kWh/m2 

Martinez 

Most efforts for reducing energy use and costs in hospitals focus on windows, insulation, and technical systems for energy recovery (Morris 1995, Dokka 2009, Holmes 2007). These energy efficiency measures achieve some important results, but are not hospital-specific. If we, in addition to use this new knowledge of energy efficient buildings, could design a hospital where its services (functions) were planned in an energy efficient manner, the result

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would be a substantial reduction in the future energy demands of hospitals. The many special activities inside a hospital provide challenges to these traditional energy efficiency measures, but also provide opportunities for new ways to improve energy performance. To achieve this we need more specific knowledge about real hospital use. When are the different parts of the hospital in use? What is the right quality of air, hot water, temperature and light?

Some hospital planners and architects already use activity models to improve patient flow through the many departments, for logistics and also for staffing. The technical building disciplines, however, have not yet embraced this approach. With activity modeling, HVAC and electrical engineers have an opportunity to supply energy which follows actual demand much more closely than in today’s hospitals.

Recent research into hospital energy efficiency has looked into the variety of activities going on in a hospital and how peak activity can differ very much both between different parts of the hospital and during the day and night. These research projects points to the need to deliver air and light that are balanced for the actual use of the hospital areas. (Targeting 100 2010, Brett 2009, Keur HosPilot (ICT), Legacy health system, Oregon). Some research projects are also concerned about the misfit between planned and achieved energy in hospitals (prof Yoshino 2008-2012). The problem is pointed out but the specific description of the activity profile of the different parts of the hospital is meager.

The aim of our study was to investigate these postulates:

There is a great variation in activity levels between different parts of a hospital, also between different times of the day, week, and year

The different functional areas have different energy signatures with respect to type of energy usage: electrical, heating or cooling.

Hospital-specific requirements drive up energy use. Today's energy systems do not follow the actual activities going on in the hospital

area.

The main hypothesis we wanted to test was:

Hospitals are much diversified ranging from functions with a highly monitored environment to quite simple areas. The activity varies from normally office hours to round-the-clock presence. Some activities going on in the hospital demand a lot of energy. The greatest potential to lower energy use is connected to monitoring the demand and a design which adjusts the energy delivery to the actual activity for the different parts of the hospital.

A goal of reduction in energy consumption by 50 % requires a new approach which looks beyond the building and its technical systems for lighting and HVAC (heating, ventilation, and air conditioning). These must be designed in tandem with the programming of the hospital functions and the specification of how the hospital is used, so that ventilation systems and lighting can match the internal life of the hospital. 

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1.2 Low Energy Hospitals research project 

The "Low Energy Hospital" project is funded 50% by the Norwegian Research Council (NRC), with the 6 private and institutional partners providing the rest of the funding. It runs over 4 years and started in autumn 2010. The goal is to provide design guidelines for new hospital designers which will lead to a halving in specific delivered energy from 2010 levels.

The project is what NRC defines as ‘user-directed’ research and is chaired by Norconsult, a consulting company working with construction project. SINTEF, Norway's largest free-standing research and consulting group, contributes with expertise in building and planning of health services.

The research project is divided into three phases. This article shows results from the first phase of the project. 

I. Phase one has been a study of the state of the art of energy design solutions in hospitals today, screening what projects are currently studying energy consumption in buildings and review of articles on the topic.

II. Phase two is now in progress, and comprises the development of a simulation model where different energy efficient design measures can be tested and quantified.

III. Phase three will conclude with specific proposals of reducing energy consumption in Norwegian hospitals with 50 % and give guidelines how this could be incorporated in the early phase planning of hospitals.

2 Research methods and data 

The method used to study the state of the art in hospital energy performance and design is summarized below:

Reference hospital selection: Three reference hospitals within the South-East healthcare organization (Helse Sør-Øst) were selected as reference hospitals. One of the reference hospitals is quite new (2009), another one is over ten years old, and the third is over 30 years old. This selection was intended to cover different building techniques, different control systems and different norms for ventilation, light and working conditions. One of the reference hospitals is a large university teaching hospital with a high percentage of research areas and advanced equipment, one hospital is on a specialty level just beneath the region hospitals and one hospital is more like a local hospital. The classification system1 of Norwegian hospital was used to assign all rooms and areas a specific function.

Clinical activity data collection: Anonymized patient data was gathered to characterize activity levels in the hospitals over the course of a day, week, and year. Together with planning data, this was used to describe the activities in the hospitals, patient treatment and personnel on duty and show how many hours, day and night and through the year, the different areas were in use and the intensity of that use.

                                                            1 Veileder Klassifikasjonssystem for sykehusbygg, Versjon 3.0 desember 2011, IS‐1965, Health Directorate of Norway 

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Energy data collection. Register actual energy consumption data from the hospitals; measured energy consumption (thermal and electrical) both for the building as such and for the equipment inside. None of the hospitals had unique meters showing the energy use for different functional areas. The existing energy meters measured building or floor-level consumption. This data was used to extrapolate energy consumption at the level of functional area. Other important inputs were outside temperature, inside working temperature, the load on different equipment, the area of the function, the area of the building part which was monitored, and design parameters for ventilation air changes for different functions. 

Actual measured energy data was gathered from the energy management system Energinet2 (Cebyc). Design data on the technical systems was provided to the project by staff from the technical divisions in each of the three hospitals. This information included number and type of equipment, and their anticipated use of energy when running. A short version of the data and findings was first presented in a report in 2011 (Martinez 2011).

Two all-day work shops were arranged with professionals from the involved hospitals and invited outside experts to discuss hospital design requirements and energy consequences. These meetings looked into how the newer hospitals are actually performing. Were technical solutions performing as hoped? What was the role of energy planning? Experts presented the latest technology concerning ventilation and lighting. Other themes were; the working environment in hospitals, future treatment techniques and an evaluation of how the need for clean air and rooms was understood by hospital personnel, projecting engineers and hospital planners. The results from one of the workshops were afterwards presented in a separate report. (Rohde, et al 2012)  

3 Results and proposed best energy practices 

The following sections discuss results and proposed best energy practice which will be tested during the next phase of the research project.

3.1 Variation in activity and occupancy levels between parts of a hospital 

There is a common perception that hospitals are in use 24 hours a day 7 days a week ("24/7"). This is reflected in, for example, data from the Norwegian statistics office. Our results give a completely different picture. The data demonstrates that it is only the bed wards that have an around the clock activity and, except for the ICU, the activity level after 6 pm is low even in that part of a hospital. A design for 24/7 activity in all areas will not be energy efficient, and yet this is the norm even in newer hospital design. One reason for this persistence is that hospitals designers (and planners) may be confusing 24/7 preparedness with actual activity.

By studying the activity data for the involved hospitals and interviewing leaders of the departments, it was possible to describe when there were patients and personnel or just personnel in the different parts of the hospital. The two largest hospitals had already organized their areas according to a new Norwegian classification system of hospital area.                                                             2 www.cebyc.no 

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The area of the third hospital was organized by SINTEF according to this system, to be used in our investigation. (Rohde 2011, Brukstid)

We divided the hospital into functional groups as offices, bed wards, patient hotel beds, outpatient and day treatment areas, operating theatres, radiology, other laboratories, main kitchen, central sterilization unit and different non-medical areas.

The results showed that outpatient departments and units doing day treatment started with only a few patients at 8 am, reached a peak at about 11 am and then started to close down at 3 pm. For bed wards the activity measured by the number of inpatients coming to the ward showed that they mostly came in the middle of the day and very few came in the weekends. Looking through the year the activity dropped 30-40 % in the vacation periods, and the summer vacation lasted for 8-9 weeks with the largest drop of activity in the middle of this period.

Surgical operating units were on duty evening, nights and in the weekends. The same was the situation for the radiology department and some chemical laboratories. But the number of personnel present at late evenings, nights and weekends drops to about 3-7 % of the numbers present at daytime. The number of personnel in bed wards normally drops by 70 % of the peak daytime number when it came to evenings, nights and weekends. Main kitchen, sterilization units, internal transport and services closed down around 6-8 pm. Hospital office areas followed a schedule, with some individual exceptions, similar to most public offices.

All three hospitals were originally designed under the assumption that they were to run 24/7. The oldest hospital had managed, only in recent years, to install control systems to modulate some of the ventilation and light to correspond to the actual use of areas, using clock- and calendar-based control.

When dividing the net area of the two biggest hospitals in our investigation, Figure 2 shows how the area is used. The areas used 24/7 is a bit under 20 % of the total for one of the hospital and a bit under 30 % for the other. 45 % of the area is used only in daytime, which is from 8 am to 4-5 pm. (Rohde 2011, Brukstid table 1) 

Figure 2 The net area of two hospitals after what hours they are in use, 2010

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Our results show that actual usage for hospital buildings is far from the commonly cited 24/7. As a consequence of all of the above, our results also show that simultaneous occupancy rates seldom are above 65% in the daytime. The many non-clinical rooms in treatment areas have a maximum simultaneous occupancy level of about 35 %.

Best energy practice: Recognizing the large variation in activity will allow designers to justify and design more energy-optimal, and correctly dimensioned, ventilation, heating, and lighting systems (Rohde 2012). This knowledge is also important when organizing the functional areas in the building. Office areas, as an example, should ideally not be spread out and placed in between functional areas with very different usage patterns.

3.2 Different energy signatures for different functional areas 

When working with data from our reference hospitals we have found that the use of energy varies much between the different functional areas. Operating theatres, ICU and sterilization vary around 480 kWh/m2. Normal bed wards and patient hotel uses 260 kWh/m2 and the office areas uses 160 kWh/m2. That indicates that it could be misleading to have one rule as to energy consumption per m2 for hospitals. The not so complicated hospitals could appear as the winner and the more complicated as the looser, despite the more complicated could have done more to use less energy than the other. It would be fairer if the demand directed towards hospitals took into account the area of the hospitals used by different functions with different need for delivered energy (Martinez 2011). Our findings also indicate that it must be done some correction for hospitals that do services for other hospitals. That could be deliveries from the main kitchen, sterilization services, giving data server support and the like.

How to reduce energy will be different for the section with operating theatres and the office area. That includes both a discussion of working procedures, the use of technique as a substitute for too liberal working procedures, the internal organizing of rooms and the ventilation techniques used.

0.00%5.00%

10.00%15.00%20.00%25.00%30.00%35.00%40.00%45.00%50.00%

Share of total m2, A

Share of total m2; B

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Best energy practice: An activity model at the room level will aggregate energy consumption to higher levels, such as functional sub-area, and functional area. These statistics will help future designers to estimate loads and to choose more optimal designs.

3.3 Hospital­specific design requirements drive up energy use 

Hospital-specific functional design requirements (or guidelines) were found to have significant consequences for energy consumption.

I. Normally patients need a higher room temperature than the working personnel; this is a challenge for the designers of technical systems.

II. Increased daylight through more window area gives a better environment both for patients and personnel but increases heat loss.

III. The ventilation system in a hospital must deal with smell, secure clean working environment for different activities, protect personnel and visitors against infected patients and protect patients against infections caused by personnel and devices used in the treatment process.

IV. Some sections in a hospital must have surfaces that can be totally cleaned. V. There are much use of water with a high temperature range from the one needed for

sterilizing equipment to drinking water.

In particular, it was found that there were several conflicting design guidelines for ventilation. There are few public regulations aimed at hospitals and their buildings. One is that ventilation should achieve less than 100 particles per m3 (cfu/m3) in operating theatres, and if the operating theatre should be characterized as an ultraclean room the number of particles should be lower than 10 cfu/m3. Apart from that the hospital law states that it should be possible to perform safe health care on the premises, without a more particular specification of what that demands of the milieu for patients and personnel. (LOV 1999-07-02 nr 61)

In projecting hospitals much of the decisions and proposals are based on international guidelines as CEN, DIN, HTM and ASHRAE for ventilation, which differs quite a deal as to what is proposed. With this vague but demanding formulation, particularly the construction of ventilation systems can be a challenge. It is the quantity of delivered air that decides most of the need for energy and it is important to have openings and channels sufficient to bring enough air into the most demanding sections. Normally projecting engineers will dimension the supply of air, heat and cooling at the margin, leaving small reserves if the future would demand more.

For light there are no international or national guidelines. The trend is to take down the background light and use devices that bring the necessary light to the spot where it is needed. It is not only the strength of the light that is important, it should have the right color too if used for certain consultations and tests.

The workshop revealed that hospitals have some of the worst working conditions of Norwegian buildings, primarily because of too high temperature, dry air and too little possibility for the employees to control the temperature. People is liable to accept a warmer

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working environment in summer and colder in winter, and it would be preferable that people used the clothing more to adapt to different temperatures.

Best energy practices: The first challenge in programming optimal solutions for areas demanding extra clean air is that few professionals, both on the engineering and the medical side, have a clear understanding of what to protect and against what. Is it the patient that needs protection against personnel or equipment carrying bacteria or is it personnel and visitors that must be protected against patients carrying contagious bacteria? Is it the medicine or the product you are working on that should not be contaminated, or should the workers be protected against contaminated products?

It is also highly important to monitor a real situation. An air flow system could work perfectly with no one in the room but not reaching the low number of particles demanded for the room when tested during a working session. Even if the system is planned according to the procedures that should be practiced in the room the result could be lower than the expected standards. Traffic in and out of the room affects the airflows. In some cases the unwanted traffic is caused by a basically wrong organization of room and storing places for goods. In other cases it is caused by poor organizing of the labor routines.

A stable airflow is also dependent on the quality of the building. All too many isolation rooms, operating theatres and laboratories are leaking because of insufficient built quality. Therefore, a good and safe working environment, safe medical practice and low consumption of energy will be best achieved when it is brought into the project at a very early stage. Early enough to have time to discuss what is the important demands from the medical service and early enough to find good technical solutions and good working routines that supports the end goal.

3.4 Functional areas fragment, with consequences for energy use

A consequence of the previous finding, that hospitals lacked sensors and systems that were prepared to deliver air and light more according to need, is aggravated this new finding: that hospital functional areas which are initially homogeneous become later fragmented into smaller areas (rooms) with different usage patterns.

Workshop participants from the involved hospitals agreed that the design program for their new hospitals had mostly overestimated the need for energy demanding procedures. The development after moving into new facilities was both an expansion of the area and a clear tendency to put more equipment into rooms and develop the activities inside existing areas in a more energy-intensive way. The use of certain areas like ICU and some bed wards became more intense, demanding more supply of air. So though there was some reserve capacity in the technical systems when the hospital was constructed, this reserve was needed very early after the new hospital was running.

Another problem identified was that some high-intensity functional areas were fragmented into lower intensity functions (the opposite trend from above, but applied to a different area). Individual treatment rooms become offices, then later devolve into storage space, all the time being served by high-intensity ventilation and lighting. Over time, zones become a "swiss

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cheese" of smaller areas and rooms with varying demands. Rooms are re-purposed without new HVAC commissioning. All of this creates problems for simple zone-based demand control.

Best energy practices: Room-based energy demand-control can provide the needed flexibility. Such systems can be easily reprogrammed for new requirements.

3.5 Energy supply versus actual energy demand from activity

3.5.1 Large base load in hospital energy consumption

The activity data showed weekly variation in treatment area activity (from peak day) of about 40%, and daily variation (from peak hour) of about 70%. Actual hospital energy consumption data for treatment area in a typical week does not reflect this variation; Figure 3 below shows a very large energy base load, even during hours of very low activity. Bed wards showed a larger energy variation, closer to the actual activity level variation.

Figure 3 Measured energy consumption in treatment area, large new acute-care hospital 

 

Best energy practice: The large base load represents a huge opportunity for demand control so that energy follows activity. An activity model for individual rooms and zones will guide designers of demand controlled ventilation, lighting and other systems. Treatment areas have a larger potential for demand control, of energy by exploiting variations in usage and low occupancy, than bed wards. Ventilation and lighting have potential for demand-control. Together these account for about 55% of total real energy consumption in modern acute-care hospital. Ventilation includes both heating/cooling and electrical energy to fan motors.

Using the activity model, the HVAC designer can then identify the smallest spaces for individual demand-control: patient rooms, treatment rooms, meeting rooms. But note that corridors, vestibules etc. cannot be directly demand controlled. The designer may then choose the optimal sensing strategy for each room/space: temperature, CO2, combinations thereof. It is helpful to de-centralize technical rooms and air handling units (for ventilation). Room-based demand control will also absorb some of the uncertainty about maximum simultaneous occupancy.  

3.5.2 Lack of focus on user-controlled electrical loads

When planning a new hospital, the HVAC discipline project team usually does not have knowledge of the electrical and thermal loads caused by hospital equipment at the room level.

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Throughout the project, these engineers will base their calculations on typical electrical plug load in Watts per square meter (W/m). Only the largest equipment types such as diagnostic imaging will be considered accurately and separately, using manufacturer data. The huge variety and large number of smaller equipment are usually not modeled for the purpose of HVAC design. HVAC designers are usually not familiar with the distribution of this equipment in the various rooms, and lack information about their various usage patterns.

It is important to understand these electrical loads and their thermal counterparts. Data from our reference hospitals indicate that hospital-specific equipment consumes almost half of all the electric energy delivered to a modern hospital, and represent 15-20% of all energy consumed. The electrical consumption emerges as waste heat for much of the year, and is conservatively estimated to increase the energy load by an additional 20% due to extra cooling demand, at today’s common heat recycling levels. The consumption of electrical energy in one of these hospitals (hospital A) is shown in Table 1. (Martinez 2011 page 18)

Table 1 Use of electrical energy, by end-use, in hospital A 2010

User  % total electricity consumption 

kWh/m2 

Lighting  35 53

Fans and pumps  20 30

Equipment  45 68

SUM  100 150

The national building codes in Norway distinguish between “building energy” and so-called “user-controlled” energy demand from technical equipment, artificial lighting, and hot water, as shown in table 2 below. User-controlled energy is not directly regulated in current building codes. Completely absent from building codes is energy used for cooling of process equipment. This “process energy” is often omitted when the energy use of a building is presented. (Tehuset 2010, Keur 2008-2012). Table 1 underline the importance to have understanding of all energy consumers when planning a hospital, not only those related to the building envelope or HVAC systems. Our findings are that the user-controlled processes are an important part of the hospitals energy balance sheet and should be taken into account throughout the planning and design periods.

Table 2 Energy use regulated by Norwegian building codes

1a Local room heating  Building energy : regulated 

1b Ventilation heating  Building energy : regulated 

2   Hot water  User‐controlled: not regulated 

3a Ventilation fan motor  Building energy : regulated 

4   Artificial lighting  User‐controlled: not regulated 

5   Technical equipment  User‐controlled: not regulated 

6 a Room cooling  Building energy : regulated

6b Ventilation cooling  Building energy : regulated 

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Without enforcement by code, the energy performance of user-controlled equipment is left to the individual planners and project teams. Few of these team members are dedicated hospital design professionals, and bring their experience from many other building types. Without a proper understanding or estimate of the electrical loads, there is an increased risk of a sub-optimal thermal design for heating and cooling systems. In a workshop on energy design in hospitals, organized by our research project, hospital designers confirmed that electrical and HVAC (thermal) disciplines could be better integrated. When asked why this was not done, one involved in the thermal energy planning in one of the project's hospitals claimed it was economic reasons; it would demand more resources during the planning phase. (Rohde, et.al. Workshop 2012).

Using building codes standard values for the user controlled loads also dramatically underestimates (by a factor of at least 2) the amount of electrical energy which these items will actually consume in a modern acute-care hospital. The understated energy budget is used by many decision makers, instead of a more correct “whole building” estimate.

Best energy practices: Project energy goals should be based on “whole building” energy consumption, not on the energy budget from Norwegian building codes. Better data needs to be gathered on actual energy consumption of the user-controlled equipment in modern hospitals.

3.5.3 Lack of design focus on monitoring and controlling plug loads

Another important insight emerging from our project is that the large populations of smaller medical equipment (“plug-loads”) are relatively large energy consumers in hospitals. The large entities above 10 kW use about 11 % of the energy consumed by equipment. Equipment with 1-10 kW use 71 % and the smaller devices using less than 1 kW use 18 %. (Martinez 2011). There are almost 2000 different types of medical-technical equipment drawing electricity in our hospital.

Plug loads in hospitals are large and growing, due to increased intensity of medical equipment, each with more CPU power, screen area etc. Suppliers have not incorporated power functions as in newer office equipment. Hospital-specific equipment draws large loads also when not in active use, and the equipment is often left "on" long after it is needed.

Of the specialized devices the MRI has the highest standby consumption of energy. In standby mode it uses 40 % of its peak consumption during use. Our results indicate that all the small devices used in the ward kitchen in the bed rooms and nursing units in sum consume as much total electrical energy as the radiology department. In university hospitals there are quite a few ventilated fume cupboards and biological safety cabinets. All these devices use considerable amounts of energy, and have long working periods though usage may be infrequently, seldom daily.

Best energy practice: An activity model at the room level which distributes the plug loads into their most likely locations can be used by designers to understand the energy consequences without being overwhelmed by detail. Suppliers of hospital-specific equipment must follow the path of IT suppliers who have brought energy consumption under control without sacrificing performance. Hospital purchasers can demand energy performance levels,

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and energy classification schemes such as The EU eco-design directive should extend to medical equipment.

There is a need to start a dialogue with equipment suppliers, large and small, on ways to reduce energy consumption without interfering with clinical procedures. Hibernation modes, reduced standby power demand and quick startup are some of the techniques which have been successfully implemented in other high-tech equipment.

3.5.4 Lack of sub-metering of energy consumption

Even large new acute care hospitals are not budgeting and designing for detailed energy metering. Energy consumption will only be available at the level of entire buildings or wings, making practical energy management much less effective.

Current metering design practice does not distinguish between the various electrical energy loads, such as lighting vs. medical equipment. This lack of distinction precludes component-based energy monitoring which would allow energy managers to track down faulty equipment, or devices left on unintentionally.

Best energy practice: Advances in wireless technology make measurement data collection cheaper and easier to integrate into a complex building project, and more flexible with respect to design changes. With more detailed data available, more efficient control strategies can be tailored by functional area, substituting today's practice of building a wing with a diversity of functions.

3.6 Consequences for passive house and net-zero energy hospitals of the future With the many processes going on inside a hospital, most of them producing heat and then leading to the demand for cooling, the looming requirement to build to “passive-house” levels may cause a sharp demand in cooling load. The heat would then be closed inside the building demanding more cooling. On the opposite, to steer the airflow efficiently it is important to have building milieus that are stable. The challenge should then rather be to organize the different functions in the hospital so the heat produced in one area could be used in another or stored for colder days. Even for Norwegian hospitals it could be a goal to have solutions that make it unnecessary to supply the hospital with heat, using the heat produced inside the hospital.

On the bright side, the large amounts of waste heat can be recycled and stored for later use. Large facades and rooftop areas in hospitals can be exploited by photoelectric or solar thermal panels to produce even more energy. Combined with good recovery, hospitals may well be the first of a new breed of “Net zero energy” buildings.

4 Discussion The findings in the first phase of this Low Energy Hospital research project support the hypothesis that the potential for a 50 % reduction in hospital energy use is present, if the planning also includes the programming of the core business of hospitals, the treatment of patients. It gives support to other studies that describes hospitals as very diversified as to what

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kind of activity is going on, when the activities take place and how intense they are. What is new with our research is that we indicate that the demands from the medical and health care professions also should be questioned, and have managed to divide the hospital into different functional parts with their specific needs. The safety of patient treatment should not be compromised, but it is useful to involve the hospital professions in the planning together with the technical professions in an early phase of the planning to secure good solutions.

First and foremost we have underpinned the thesis that bringing in activity based supplies of ventilation and electricity will make it possible to monitor the use of energy toward the goal of 50 % reduction compared to the situation in 2010.

One important assumption in planning hospital is that with all its diversities it should be planned as a city. A hospital is not one entity, not one or more buildings, but a town with a diversity of needs and possibilities. It has dwelling areas, industrial areas, administrative office areas and what could be called shopping areas. Their demand for temperature, daylight, security, cleanliness, amount of air supplied and so on differs considerably.

Safe treatment conditions are a must, but it is also part of low energy solutions to see technical solutions together with working routines and a thorough understanding of what should be protected against what. In an operating theatre the patient will mostly be the one without any infections of any kind while the personnel and the equipment is the source for contamination of the operation wound. In most isolation units the problem is opposite. It is the personnel and visitors that should be protected against the infected patient. This could be discussed more broadly. Here it is important to stress that these problems must be discussed and understood in a very early phase of the hospital planning process.

There may be some contradiction between letting personnel regulate their working climate vs. more central monitoring of temperature and light. On the other hand tests have revealed that people endure a wider temperature range when given the possibility of some control. When planning the technical systems it could also be relevant to remember that some simple manual techniques are also energy-effective. In rooms that shall be clean the number of air shifts should be about 20 an hour. Opening a window equals to 28 air shifts an hour. For some parts of the hospitals it could then be just as safe and more energy efficient to open the window if the need arises.

Planning a hospital is a complex task. The optimal hospital do not exist, it is needed to do compromises. Bringing energy consumption in as a new prioritized goal makes it even more complex. Our findings strongly indicate that the technical solutions of energy delivery should be far more evidence based than today, and the evidence it should be based on is the activity profile of the hospital and a well-defined demand for air quality and on demand deliveries.

5 Conclusion The first phase of The Low Energy Hospital project has in full supported the thesis that it is possible to reduce the energy consumption of Norwegian hospitals by 50 % compared to new hospitals in 2010. A university hospital from that period consumes about 400 kWh/m2 in

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whole-building energy. The new Norwegian building codes require between 300 to 330 kWh/m2 for hospital buildings, excluding energy for medical equipment and internal processes. That is the highest for all types of buildings in Norway. Our design goal is therefore 200 kWh/m2 in whole-building energy.

The most potent of all techniques to reach this goal is to prepare the hospital for on demand delivery of electrical energy to equipment and ventilation energy, using demand control methods. Activity modeling is a very useful design methodology to show where, and how, demand control designs may be applied. 

6 References: Rabl A., Norford L.K. (1991) Peak load reduction by preconditioning buildings at night, International Journal of Energy Research, Vol. 15, 781-798

Advanced Energy Design Guide for Small Hospitals and Healthcare Facilities, (2009) ASHRAE Special Project 127, American Society of Heating, Refrigeration and Air Conditioning Engineers, ISBN 978-1-933742-66-3

Behovsstyrt ventilasjon, (2005) Byggforskserien, Byggdetaljer, 552.323, Sending 1

Bonnema E, et.al. (2010) Large Hospital 50% Energy Savings: Technical Support Document; The National Renewable Energy Laboratorium/Technical Report 550-47867, September

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