Sunspace Augmented Positive Ventilation at Ballantrae

Evaluation Report Sunspace Augmented Positive Input

Ventilation at Ballantrae

John Currie

2005

Report

in respect of Sunspace Augmented Positive Input Ventilation at Ballantrae

for

Ayrshire Housing

Building Performance Centre

School of the Built Environment 10 Colinton Road, Edinburgh, EH10 5DT

Tel: 0131-455-2253

January 2005

PREAMBLE 1.0 Objectives

1.1 This report was commissioned by Mr Jim Whiston of Ayrshire Housing (the Clients) from the Building Performance Centre with the following objectives:

To carry out monitoring and evaluation of the Positive Input Ventilation installed under the Scottish Clean Energy Demonstration Scheme (SCEDS) at Craigie Mains, Ballantrae

2.0 Restrictions

2.1 Copyright in this report and all associated notes etc. is retained by the Building Performance Centre.

2.2 This report and the associated items have been prepared for the exclusive use

of the Client and are confidential between us. It has been prepared solely for the specific purpose to which it refers. It may be disclosed to other professional advisors assisting in respect of this purpose. It shall not be disclosed to any other party, be duplicated or be published in any way whatsoever, without our written consent. Any such party relies upon the report at their own risk.

2.3 The Building Performance Centre accepts no responsibility for any losses

incurred as a result of any decisions made on the basis of the work reported herein.

Building Performance Centre 31/01/2005 Ayrshire Housing Page 2 of 22

3.0 Positive Input Ventilation System A total of 16 NuAire ‘Ecosmart’ positive input ventilation (PIV) units were installed in the new build housing development at Ballantrae utilising a glazed sunspace on the south elevation of each dwelling to augment the energy saving potential of the installation (Plate 1).

Plate 1 South elevation showing glazed sunspaces The Ecosmart units supply ventilation air to the dwelling with the air being drawn from the attic space, sunspace, or outside, depending on the user setting – typically the warmest source of either sunspace or attic during the heating season and cooler outside air during summer months. The Ecosmart units were located in the attic space and connected to the various supply sources using insulated flexible ductwork (Plate 2). Thermistor temperature sensors were installed in each of the inlet ducts and house to enable the system controller to select the appropriate ventilation source for the desired conditions.


Plate 2 Ecosmart unit showing connected ductwork

4.0 Monitoring The original proposal was to install NuAire monitoring equipment in 8 no. dwellings

which would enable assessment of the energy benefit to the property derived from the delivered air temperature, outside air temperature, delivery flowrate and occupant control setting.

It was proposed to establish two of these dwellings as 'controls' - disabling the

sunspace solar collection element and operating the systems as normal positive input ventilation systems. Additionally, an attempt was made to evaluate the system benefits relative to occupant comfort; by installing additional monitoring equipment to monitor temperature and relative humidity in the occupied zone of three of the dwellings. A questionnaire survey was to be undertaken in support of this.

5.0 Data Collection

A total of 14 NuAire NiCM Link data loggers were eventually installed in the properties together with 3 additional Grant Squirrel temperature and relative humidity loggers. A software upgrade to each system delayed the start of the monitoring period until the 4th July 2003 after which commenced a one-year monitoring period. Problems were experienced in a number of properties which resulted in incomplete data sets; this was mostly due to the tenants switching off the ventilation units and


disabling the data collection system and one property experienced a change of tenant part way through the monitoring programme. In another dwelling the tenant reconfigured the ducting installation; negating the control configuration. However, high volumes of data, recorded at 10 minute intervals, were collected for subsequent analysis and the data monitoring was continued until November 2004 in selected properties. Questionnaire survey forms were sent to all 16 residences on 9th July 2004 in conclusion to the main monitoring exercise. The 9 responses received are given in Appendix 1 at the end of this report.

6.0 Data Analysis

6.1 Ecosmart Performance The onboard programmable interface control software and volatile memory enables each NuAire Ecosmart device to log up to 6 months temperature and activity data. This included:

House Temperature Sunspace (Solar) Temperature Loft Temperature Outside Temperature Ecosmart Delivered Temperature User Demand (Target) Setting

A typical profile of this data is shown in Fig. 1 where the target setting is that obtained from a potentiometer dial located on the Occupant Ecosmart Control (Plate 3) and can be set by the between cold and warm depending on comfort requirements. This is recognised as a signal measured between 5 (cold) and 50 (warm) on the graph. 6.2 Control In order to establish the control houses the sunspace supply duct to the Ecosmart unit was disconnected with the sunspace temperature sensor left connected. This enabled the Ecosmart units to operate in standard Drimaster positive input ventilation mode. The energy benefits on the Drimaster positive input ventilation system had previously been validated by the Building Research Establishment (BRE) in their reports CR 106/99 and 379/99 as 550 kWh over a heating season. House numbers 24 and 38 were selected as control dwellings.


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Fig. 1 Typical weekly data profile

Plate 3 User control panel


6.3 Energy Performance The energy benefit gained by using the sunspace to pre-heat the ventilation air was calculated from the supply volume (mass flowrate) multiplied by the specific heat capacity and time integral of the delivery/outside air temperature difference. This is illustrated in the daily temperature profile in Fig. 2 below where the energy benefit to the house of the positive input ventilation over infiltration ventilation is represented by the maroon shaded area.

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Fig.2 Typical daily temperature profile showing energy saving

It should be noted that the maximum energy benefit from the sunspace, represented by the yellow shaded area, is nor being realised in this example and it is suspected that either a thermistor calibration problem or some leakage past the outside air/attic inlet damper may be causing this. For the control houses the energy gain was that obtained solely from the attic space, as the sunspace input to the system had been disconnected. A graph showing how the energy benefit was represented can be seen in Fig. 3 where the supply temperature very closely profiles the attic temperature; although much less than the sunspace augmented system an energy saving, represented by the maroon shaded area, is still evident.


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Fig. 3 Typical daily profile showing energy saving from ‘control’ dwelling The energy benefit was derived over a heating season for each dwelling and the results presented in Table 1 below. Due to the aforementioned problems some of the data sets were incomplete and the energy savings from the system could not be calculated. Where available, these are presented alongside the annual energy consumption for each dwelling taken from metered data. The average house temperatures recorded are included to give an indication of the levels of occupant comfort in each dwelling. The average energy benefit gained through the installation of sunspace augmented positive input ventilation is of the order of 1500 kWh per annum over traditional infiltration / mechanical ventilation systems. This is more than double the energy savings available from the attic derived positive input ventilation (770 kWh) as delivered by the control house. Comparing this with the total energy consumption of the dwellings it accounts for a saving of 9.8 % and when compared to the average heating requirements the saving is 14.3 %.


Dwelling Type

Annual Energy

Usage (kWh)

Off-Peak Heating (kWh)

Energy Saving (kWh)

Average Temperature

(oC)

No. 7 3 bedroom, asymmetric 21,722 16,746 1561

23.8

No. 20 3 bedroom, asymmetric ** **

1534 24.7

No. 24 (control) 2 storey, 2 bedroom 11,820 8,654 770 21.8

No. 26 2 storey, 2 bedroom 13,499 7,916 1172 19.4

No. 32 2 storey, 2 bedroom 15,766 9,817 ** **

No. 36 2 storey, 2 bedroom 14,246 9,600 ** 22.2

No. 38 2 storey, 2 bedroom 12,589 7,909 ** 21.3

No. 40 3 bed wheelchair access 18,286 13,142 1763 20.6

Average 15,418 10,541 1507 21.9

Table 1 Summary of Annual Energy Usage and Savings (** denotes incomplete or corrupted data sets)

6.4 Occupant Feedback A questionnaire survey of all the occupants was conducted in order to obtain some user feedback regarding the operation of the ventilation system, together with some indication of improvements in general comfort and wellbeing since moving in to the property - most of the occupants had moved from older, less well insulated and energy efficient, dwellings. The questionnaire comprised a mix of quantitative and qualitative responses as is shown in Fig. 3 below:


Ballantrae Survey Questionnaire

Please complete the survey form below and return in the reply-paid envelope to: John Currie, School of the Built Environment, Napier University, 10 Colinton Road, Edinburgh, EH10 5DT. Present Electricity Meter Reading ( 2 meters located in under-stair cupboard )

Left-hand Meter Reading Right-hand Meter Reading Please circle as appropriate 1. Do you understand how the house ventilation system operates? Yes No 2. Do you understand how the house heating system operates? Yes No 3. Do you use the ventilation system controls? Often Sometimes Never 4. How effective do you feel the sunspace is? Ineffective 1 2 3 4 5 Effective

(circle 1-5 as appropriate)

5. In comparison with previous houses; does this one feel Colder 1 2 3 4 5 Warmer

(circle 1-5 as appropriate) Stuffy 1 2 3 4 5 Fresher

6. Are there any asthma sufferers in the family? Yes No 7. If so, have their symptoms improved since moving into the house? Yes No 8. Do you ever notice any condensation on bedroom windows? Yes (e.g. in the mornings) No 9. Is the house expensive to heat? Yes No 10. Approximately how much do you spend on electricity? £/month £/quarter Please add any comments you would like to make, below

Fig. 3 Questionnaire to occupants


From a total of 19 questionnaires sent out 9 completed responses (47%) were returned. The responses are summarised below: Whilst the majority of households (88%) understood how their heating system operated, an equivalent percentage (88%) indicated that they did not understand how the house ventilation system operated. This is interesting as the contacted installer explained the operation of the system at the time of installation; this information has either been forgotten or not passed on to other members of the household. When asked about use of the ventilation system controls, 56% of the respondents indicated that they used the controls often, 22% sometimes and 22% never. Over the course of the monitoring period it has been noted that progressively more of the ventilation systems were being turned off (devices failing to data log and communicate). By the end of the monitoring period nearly all of the systems had been switched off. It is suggested that all of the systems be re-commissioned and a simple one page summary of the system operation and its benefits be produced and given to each household. Semantic 5-point differential scaled questions were used to enquire about occupant comfort and effectiveness of the sunspace. Generally speaking, the occupants found the dwellings warmer (3.4) and fresher (3.1) than previous houses they had lived in although most (2.5) felt that the sunspace was less than effective. Comments received indicated that this was in-part due to leaks in the glazing causing water ingress and the fact that the space overheated in summertime. The ventilation system extracts heat from the sunspace only when it is warmer than the other two inlet supplies (attic & outside) and the user control is set for heating. During the summertime, when the user control is set for cooling, air would not be drawn from the sunspace during daylight hours and this can result in high temperatures (> 40oC) being experienced. The inclusion of an openable window at a high level within the sunspace would provide the occupant with control over such conditions. The ventilation system incorporates G4 grade air filters which can arrest particle sizes down to about 5 microns; this includes for instance asbestos fibres, cement dust, plant spores and pollens and some bacteria. As the dwellings have the added benefit of being supplied with filtered air the study enquired whether there were any perceived health benefits noticed by occupants; particularly those who might suffer from respiratory problems e.g. asthma. Of the respondents, 56% indicated they had asthma sufferers in the family with 33% noting an improvement in their condition since moving into the house. Condensation forming on windows overnight can often be associated with inadequate levels of heating and/or ventilation in the dwelling (assuming average rates of moisture evolution). Most of the respondents to this question (67%) indicated that no condensation was present. Of those that did notice condensation, on checking back through the data it was identified that these houses had switched off the ventilation systems at varying times throughout the year.


The last two questions were included in order to gauge the occupant’s perception of energy usage and the relative cost of that energy. Opinion was evenly divided on the relative expense of heating the dwelling and the figures provided for average monthly/quarterly electricity billing did not appear to correlate with the metered consumption. Some occupants indicated that they had never received a utility bill. When looking at the earlier Table 1 significant differences in occupant comfort levels, as identified by average house temperatures, have a bearing on these costs. All of the respondents took the opportunity to make additional comments on the questionnaire; in summary these indicated a lack of understanding/instruction in the operation of the heating system and that the sunspace was too cold in winter and too warm in summer.

7.0 Conclusion

The ventilation systems installed at Ballantrae were designed to enhance the already well-established system of positive input whole-house ventilation by use of a glazed sunspace to augment the heat recovery potential. The monitored data showed that using the sunspace in this configuration can save up to 15 % of the domestic heating requirements when compared with traditional infiltration ventilation, and more than doubled the energy benefit of that obtained by positive input only ventilation. Occupant feedback suggested that the sunspace overheated in summertime and this is borne out by the monitored data; which shows temperatures in excess of 40 0C being recorded in the sunspace. The inclusion of an openable window at a high level within the sunspace would provide the occupant with some control over such conditions. Many of the occupants indicated a lack of understanding of how the ventilation systems operated. This resulted in many of the systems being switched off with the attendant problems this causes with moisture displacement, some tenants noticing condensation on windows, and in data collection. It is recommended that all of the ventilation systems be re-commissioned to ensure correct operation and a simple data sheet explaining the system operation and its benefits given to each household.


Appendix 1


Sunspace Augmented Positive Ventilation at Ballantrae

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