Ventive humidity report

HUMIDITY IN DWELLINGS WITH VENTIVE POST OCCUPANCY EVALUATION REPORT MIGUEL ÁNGEL FUENTES LLANOS TOM LIPINSKI 30TH MAY 2014

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1. EXECUTIVE SUMMARY This document assesses relative humidity levels in three occupied dwellings with a full house Ventive PVHR (Passive Ventilation with Heat Recovery) system. It describes the monitoring approach, provides regulatory background to humidity levels in dwellings and gauges the indoor air quality in light of the regulations.

As can be expected in dwellings with continuous ventilation with heat recovery humidity levels are below the regulatory maximum in all cases while remaining at the lower end of the range recommended by CIBSE. Besides the collected data, the qualitative feedback from the tenants described the indoor air quality as good or very good.

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2. INTRODUCTION This report collates humidity data collected from 3 dwellings following the installation of Ventive PVHR ventilation system (Passive Ventilation with Heat Recovery).

Data loggers have been supplied by Energence, who are also providing the post occupancy monitoring (POE).

Energence is an independent third party organisation engaged to monitor Ventive installations with monitoring including ventilation flow rates, indoor, outdoor and duct air temperatures, indoor and outdoor humidity and indoor CO2 levels (Figure 1). This report concentrates solely on humidity within the observed dwellings.

Figure 1: Data Logger inputs

The following locations have been included in this report: 1. Greenwich, London. This period property is owned by Royal Borough of Greenwich and has a history of damp and mould. As part of the void refurbishment, a full house PVHR system from Ventive was installed combined with minor airtightness measures. No other energy reduction retrofit work was considered.

Monitoring is installed in the only bathroom, which is located on the ground floor of the property.

2. Watford, Hertfordshire. Privately owned bungalow which has undergone a partial energy reduction retrofit with some airtightness and insulation measures installed concurrently to Ventive PVHR system. Monitoring is installed in the open plan kitchen on the ground floor of the property.

3. Larnaca (Cyprus). Privately owned modern property with a reasonable airtightness. No specific energy reduction work undertaken in addition to Ventive installation. Monitoring is installed in the open plan kitchen on the ground floor of the property.

3. GUIDANCE AND REGULATIONS REGARDING HUMIDITY 3.1 CIBSE: CIBSE Guide A (Environmental design) [1] states that humidity levels in dwellings in the range 40– 70 % RH are generally acceptable, with lower humidity often acceptable for short periods. According to the Guide A, humidity of 30% RH or below may be acceptable but precautions should be taken to limit the generation of dust and airborne irritants and to prevent static discharge from occupants (CIBSE Guide A, chapter 1.3.1.3).

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House dust mites prosper in warm damp conditions providing there is a supply of food in the form of human skin. Mites can be controlled if their immediate microclimate can be maintained below 73% RH. Buildings in which there are prolonged high air humidities are likely to experience problems such as airborne fungi and house dust mites, particularly if room humidities exceed 70% RH for long periods. Allergies and respiratory illnesses have long been associated with mould growth and moisture, particularly for asthma and rhinitis (CIBSE Guide A, chapter 8.3.1).

3.2 Building Regulations: Approved Document F [2] - Section 4, Introduction to the provisions states: “The key aim of the requirements of Part F1(1) is that a ventilation system is provided that, under normal conditions, is capable of limiting the accumulation of moisture, which could lead to mould growth, and pollutants originating within a building which would otherwise become a hazard to the health of the people in the building.”

(Approved Document F, chapter 4.2) The maximum humidity levels are set as per table below (Approved Document F, Appendix A):

Table A2 Indoor air relative humidity Moving average period

Room air relative humidity

1 month

65%

1 week

75%

1 day

85%

For the ease of assessment the recommended RH range from CIBSE Guide A, and the maximum daily RH average from the Appendix A, Part F, Building Regulations have been superimposed onto performance graphs as datum points.

4. OBSERVED HUMIDITY LEVELS 4.1 GREENWICH SITE The system monitored is a Ventive S+ with two Ø125mm insulated flexible ducts acting as air supply and extract channels. The only window in the bathroom remains closed for most of the day, apart from occasional 20 minute periods in the morning (and only during the shower).

The dwelling was unoccupied for the first month of the monitoring period. With no internal source of moisture, humidity remains low. Within two weeks after the new tenant moved in, the humidity stabilises within the 40% - 50% band.

Figure 2 and Figure 3 demonstrate internal and external humidity levels between early March and mid-May 2014:

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Void Property

Occupied Property

Figure 2: Historical Data – Greenwich Installation (March to April)

Figure 3: Historical Data – Greenwich Installation (April to May)

As can be seen above, over the period of 5 week period 70% humidity is momentarily exceeded in eleven instances, in all cases receding back to 50% within an hour. At no point does the relative humidity reach the maximum average levels as set out in Part F of Building Regulations, remaining well within acceptable levels.

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When humidity levels are assessed against exhaust air velocity, the relationship appears closely correlated and inversely proportional. In short, the higher the extract ventilation rate the lower the observed level of humidity (Figure 4 below):

Figure 4: Internal Humidity vs. Extract Velocity – Greenwich site.

4.2 WATFORD SITE Watford site has two Ventive S+ installed and the monitored system has two 204x60mm rigid ducts acting as supply and extract channels (providing an ‘equivalent’ ventilation area as 5 inch round duct of 11,200mm2).

Figure 5 and Figure 6 illustrate the levels of internal and external humidity from April to mid-May 2014:

Figure 5: Historical Data – Watford Installation (April)

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Figure 6: Historical Data –Watford Installation (May)

Similarly to the Greenwich site, while external humidity oscillated between 30% and 100%, internal humidity remained within the 40% to 60% band, within both CIBSE recommendations and Part F requirements.

4.3 SITE IN LARNACA The system installed in Cyprus is a hybrid Ventive S which is installed in an open plan kitchen. Figure 7 to Figure 9 below display relative humidity levels observed between mid-December 2013 and mid-May 2014:

Figure 7: Historical Data – Larnaca Installation (December to February)

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Figure 8: Historical Data –Larnaca Installation (February to April)

Figure 9: Historical Data –Larnaca Installation (April to May)

In Cyprus external humidity levels oscillate between 20% and 100%, with the internal humidity remaining mostly within the 40% to 65% band. The higher indoor humidity can be attributed to a much reduced scope for heat recovery in Cyprus, with external temperatures much closed to indoor temperature than in the UK.

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With a lower increase in the temperature of the incoming fresh air there is an overall lower reduction in relative humidity of the supply air flow. In general, the lower the outside temperature relative to the indoor temperature, and, by default the higher the temperature gain of the incoming air through the heat exchanger, the lower the relative humidity level of the supplied fresh air.

There is a strong correlation between internal and external humidity (Figure 10) in the building, which confirms that the room is more dependent on the ambient conditions than in the UK. Having said that, the overall indoor humidity levels remain well within both CIBSE recommendations and Part F requirements.

Figure 10: Internal Humidity vs. External Humidity – Larnaca installation

5. CONCLUSIONS As the data above demonstrates, dwellings with a full house Ventive PVHR system installed maintain low humidity levels regardless of the external relative humidity or temperature. This not only contributes to a good indoor air quality but also reduces the building fabric degradation reducing the maintenance requirements and prolonging the lifespan of the building.

6. REFERENCES [1] CIBSE (2006). Guide A: Environmental design.

[2] HM Government (2010). Approved Document F – Ventilation (2010 Edition), Planning Portal.

[3] Lipinski T., Lee S. H., and Childs P. (2013) Passive Ventilation of Buildings with Heat Recovery (PVHR) Proceedings of the 13th UK Heat Transfer Conference, pp. 941–948.

Thames House, Swan Street, Old Isleworth, TW7 6RS Tel: 02085601314

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Company Registration Number: 07721060 VAT Registration Number: 119033441

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