Performance project: Improvement of the ventilation and building air tightness performance in occupied dwellings in France

Transcription

1 Performance project: Improvement of the ventilation and building air tightness performance in occupied dwellings in France Jean-Luc Savin 1 and Anne-Marie Bernard 2 1 Aereco S.A., 9 allée du clos des charmes, Collégien, Marne la Vallée cedex 3, F 2 ALLIE AIR, 4 clos Ballet, Meximieux, F annemarie.bernard@allieair.fr ABSTRACT As we increase energy requirements on ventilation, it is essential to assess the real performance of these systems on site, both for energy savings and IAQ aspects. Applied on two new buildings located in Paris and near Lyon (France), Performance project has given the opportunity to check the feasibility of applying quality approach while building to improve performance and to measure precisely, during 2 years, in a large set of dwellings (29) the efficiency of the French standard ventilation system for new buildings (humidity controlled single exhaust mechanical ventilation). With numerous probes installed in all the rooms of the monitored dwellings, the monitoring has enabled to better understand the parameters which can influence the ventilation performance. The results have demonstrated the efficiency of the humidity controlled ventilation in managing the indoor air quality and its adaptation to occupancy by measurements of CO 2 and humidity concentrations. Energy savings on the equivalent airflow for energy have been evaluated at 30% on the monitored over-occupied dwellings; the extrapolation to the average occupancy of the French building stock have shown to be between 50 and 55% energy savings. KEYWORDS Monitoring, energy, performance, IAQ, ventilation, humidity. INTRODUCTION Achieving good performance (energy and IAQ) requires implementing quality process to build tight and to ventilate right with efficient systems. The objectives of the study were to show that: A quality process can be used to develop good practice and improve results achieved, A good air-tightness can be really achieved as long as design, product selection and installation are appropriate, Corrections, generally easy and stable in time, can be done when defaults are noted, An assessment of real performances obtained on site by humidity controlled mechanical ventilation is needed. This study has followed the construction of 2 buildings and applied a quality process including training of contractors and creation of tools, guides A full measurement campaign with probes in many rooms on the 2 sites and analysis of results were operated during the next two years.

2 QUALITY APPROACH Observing construction practice and main causes of poor results, both for ventilation performance and building tightness, has shown recurrent defaults. It is therefore essential to insert some phases in the building planning, to train the contractors, to organise intermediate and final checks in order to assess the results obtained and to follow the progression during all the building creation. A practical guide on main factors for a better air-tightness of buildings have been created and widely distributed to contractors and architects. The approach includes mainly: A description of who is doing what in the process to define responsibilities more clearly (the overall result is a multiple corporations and actors results) A cartography of all essential process during all phases of the building and a guide explaining all the actions and the actors Training guides for the most concerned contractors to improve knowledge on the subject Definition of design solutions to obtain good results (example of solutions) detailed with drawings and collected in a practical guide, both for building and ductwork air-tightness. These proposals have allowed a first discussion with the installers to define the best practice adapted to our cases. Results have been quite different between the two sites, one needing more corrections than the other to achieve a correct result. From this experience, it was really noted that the approach must start as soon as possible as the construction begins for a better appropriation by the contractors. The cost of the quality process has been estimated respectively to around 500 and 800 /flat in Lyon and Paris sites. This should decrease when used regularly to 300 /flat. This cost doesn t include the air-tightness tests. Using quality approach is needed to achieve correct performance and improve our building stock in agreement with the energy objectives of the coming years. MONITORING OF TWO OCCUPIED BUILDINGS EQUIPPED WITH HUMIDITY CONTROLLED MEV From 2007 to 2009, a large scale experiment was realised on the two studied buildings to measure the performance of the installed demand control ventilation (DCV) systems. Buildings The buildings have been erected in 2007; they are located in France, in Paris and Lyon (Villeurbanne). They present the characteristics of social housing buildings. Both have been equipped with the French standard ventilation system: the humidity controlled mechanical ventilation which is composed of humidity controlled air inlets in the dry rooms associated with humidity controlled or presence detection extract units in the wet rooms. A centralised fan with pressure control is connected to the extract units. These social housing dwellings are characterized by an occupation largely above the statistics in France, which has an impact on the energy as we shall see further.

3 Table 1 : Characteristics of the monitored buildings Paris site Lyon site Building height 8 floors 6 floors Type of dwellings From 1 to 5 main rooms From 2 to 5 main rooms Permeability Monitored dwellings Metrology and measurements I4 = Pa n50 = Pa I4 = Pa n50 = Pa 19 dwellings (5 top floors) 10 dwellings (4 top floors) The two buildings have been equipped to measure the outdoor conditions (wind speed and direction, temperature and humidity), the indoor climate parameters (CO 2, temperature and humidity) and the ventilation terminals parameters (pressure, opening sections, airflows) in all the rooms of the monitored dwellings. It is the first time that CO 2 is measured in occupied dwellings in such a large scale. Measurements have been realised during two complete heating seasons ( and ). Indoor Air Quality CO 2 concentrations The measurements of CO 2 concentrations (Figure 1) show that the indoor air quality is ensured in the low occupied bedroom (one adult) as well as in the high occupied one (four adults). The peak of CO 2 concentration has shifted from 700 ppm in the low occupied bedroom to 950 ppm in the highly occupied one, but even in that case, the 1500 ppm level is not exceeded more than a very few hours. Num ber of hours CO2 ppm concentrations B43 T3 Room n.2 4 adult B32 T2 Room n.1 1 adult Figure 1 : CO 2 concentrations in two bedrooms with different occupations (blue - square: 1 adult, red triangle: 4 adults). CO2 concentration in ppm In-situ measured with humidity controlled air inlet Simulation with a humidity controlled air inlet Fixed flow ventilation Time (hours) Figure 2 : Night evolution of CO 2 concentrations 1 Comparison between HC air inlet (measured and simulated) and fixed flow ventilation (simulated). Figure 2 confirms on a night evolution the efficiency of the humidity controlled (HC) air inlet in comparison with a simulated fixed ventilation: while HC air inlet maintains the CO 2 level below 1500 ppm, a fixed airflow would have led CO 2 over 2200 ppm. In addition, a short period (one month) with the fan stopped has enabled to observe a strong raise of CO 2 concentrations (above 1900 ppm most of the time), with no particular reaction of the occupants. This confirms the major role of ventilation on IAQ and shows 1 Measurements in a 35 m 3 bedroom occupied by two persons (door closed).

4 that occupants are unaware of poor ventilation and don t compensate for instance by window opening. Humidity and condensation risks A calculation of the condensation risk on the double glaze window 2 has shown that the HC ventilation system is particularly efficient on that side, as only a very few hours were presenting such conditions. The majority of dwellings presented a null risk; the maximum risk observed has been evaluated with 8 times / year where the condensation may appear more than one hour on the window. The rare dwellings and periods with a condensation risk all present a particularly high occupation density, and some of them have a washer-dryer releasing its humidity in the ambiance. Energy impact The energy consumption of the ventilation system is the result of the thermal losses induced by the heat of the incoming air plus the fan consumption. Energy losses due to air renewal Figure 3 present the average measured equivalent 3 during a complete heating season. airflow for energy per dwelling Airflows (equivalent for energy) (m 3 /h) Figure 3 : Statistical equivalent airflows for energy per dwelling on Paris site. Rated by dwelling types in comparison with French regulatory constant airflow (grey squares) heating period. The disparity of measured equivalent airflows results from the adaptation of the ventilation system to various occupations, activities, occupant behaviours and dwelling sizes. The comparison with the French regulatory reference (fixed airflow, grey triangles bar) shows the statistical airflow reduction thus the energy savings- obtained by the DCV systems. The measured savings on the airflow for this project is evaluated at 30%. Moreover, this good result hides actually a better one. As seen before, most of these dwellings are over-occupied, especially on Paris site. When we extrapolate this result to the statistical average French occupancy for each type of dwellings, the result is between 50% and 55% energy savings on the ventilation heat losses. This statistical 2 The calculation was based on the measured internal and external temperature and humidity. Window Ug value = 3 W/m²K (low efficiency glaze). 3 The equivalent airflow for energy corresponds to the fix equivalent airflow in terms of heat losses through ventilation. It takes into account the indoor-outdoor temperature difference.

5 airflow reduction does not affect the IAQ; on the opposite, a better IAQ in terms of CO 2 and humidity has been proved as shown before. Fan consumption An additional advantage of the airflow modulation is to reduce the average global airflow exhausted therefore the power consumption too - by the collective fan. Measurements have shown that the ventilation needs are time-dispatched so that the global airflow is at any time largely lower than the sum of the maximums. The resulting energy saving 4 on the fan consumption has been measured at 50% on Paris site, 35% on Lyon site. This results vary with the pressure set up from the control. Validation of hourly thermal-aerodynamic software An accessory purpose of the project was the validation of the hourly simulation software SIREN 5 which is used for the assessment of the humidity controlled ventilation systems in the French Technical Agreements. The measured results (airflows, CO 2 and humidity concentrations, risks of condensations, etc.) and their comparison with the simulation through SIREN have demonstrated a fairly good reliability of the dynamic tool for energy and aerodynamic simulations. Although SIREN seems to over-evaluate condensation risks (this may be due to some assumptions on room surfaces, doors and windows opening etc), this software is particularly relevant for the evaluation of humidity and demand controlled ventilation systems. Operation of the humidity controlled ventilation components One of the objectives of the project was to demonstrate the good working of the humidity controlled components (air inlets and extract units). Figure 4 : Airflow / RH behaviour of a humidity controlled extract unit in the kitchen. Pink curve = laboratory measurement. Grey lines = tolerance envelope. Dots points = measurements (light color in summer, dark in winter) The airflow / relative humidity (RH) measurements have shown that all the humidity controlled terminals have been working in their tolerance envelope, following in-situ the laboratory nominal curve, as presented figure 4in Figure 4 for an extract unit in the kitchen. The statistical 6 airflow/rh couples presented in different colours for each month show the impact of the external absolute humidity rate: the dryer outdoor air induces a 4 In comparison with the French Thermal Regulation fan consumption data for a constant airflow system. The use of low consumption fans have enabled to improve their nominal performance. 5 Developed and proposed by French CSTB (Centre Scientifique et Technique du Bâtiment). 6 80% most frequent airflow / RH points have been represented

6 lower basic indoor relative humidity which gets the extract unit close to the minimum opening. This phenomenon, already observed on various monitoring such as HR- VENT (2004), contributes largely to the ability of HC ventilation to save energy when the outdoor temperature is low. CONCLUSION The feasibility of implementing quality approach at reasonable cost on site to achieve better results have been shown as well as the possibility to correct and improve performance when first tests show too poor results. Tools, such as guidelines with detailed figures have been developed for training the contractors and increase sensibility to main risk factors. The large scale in-situ monitoring realised has demonstrated the good performance of the system to reach a high level of indoor air quality compared to a fixed flow system, thanks to their adaptation to the over-occupation. The condensation risks are negligible. The monitored systems have enabled 30% energy savings in comparison to the regulatory fixed airflow on these over-occupied dwellings. An extrapolation to the French average statistical occupancy leads to 50 to 55% energy savings on heat losses. Fans consumption have been decreased respectively by 50 and 35% on the 2 sites. The monitored humidity controlled ventilation components have shown in-situ working characteristics in compliance with the laboratory tests, and a seasonal airflow / RH behaviour favourable to the energy savings. This project has also been the occasion to validate the hourly evaluation tool (SIREN) used in France for Technical Agreements. With this new complete in-situ monitoring, humidity controlled ventilation has shown once more its IAQ performance as well as its huge potential for saving energy on the ventilation heat losses. ACKNOWLEDGEMENTS We acknowledge hereby the financial support of ADEME and the participation of all Performance partners: Coordinator: AIR.H association, Jean François NOUVEL, Laure Schwenzfeier. Partners: BOUYGUES BÂTIMENT IDF ; GFC CONSTRUCTION ; CETE de Lyon ; CETIAT ; COSTIC ; ALLIE AIR ; PBC ; ANJOS ; AERECO ; ALDES ; ATLANTIC Climatisation et Ventilation. We are grateful to CIRMAD Grand Sud, OPAC Rhône and Paris Habitat for their participation and their building. REFERENCES Air.H. (2009). "Performance de la ventilation et du bâti" Final report (2009). Ademe convention n.0504c0114. Carrie, F.R.; Fleury, M.; Voisin, G.; Aurlien, T., Stimulating better envelope and ductwork airtightness with the Energy Performance of Buildings Directive, AIVC 29th Conference, Kyoto, Japan Flourentzou, F., ; Savin, J.L. (2009) Insitu measurements to evaluate the real energy savings of humidity sensitive ventilation in Minergie buildings CISBAT Conference, Lausanne. Savin J.L., Bernard A.M., Jardinier L. ; Demand Controlled Ventilation (DCV) and Energy Savings : application on sites ; Proceedings CLIMA Wellbeing Indoors (10-14 June Helsinki), pp 8 Savin J.L., Berthin S. and Jardinier M. (2005). Assessment of improvements brought by humidity sensitive and hybrid ventilation/ HR-Vent project. 26 th AIVC conference, Brussels.