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How far should we go into the renovation process to achieve good indoor environment?
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July 31, 2012

How far should we go into the renovation process to achieve good indoor environment?

Healthy Buildings Conference, July 11, 2012, Brisbane, Australia

How many of these types of buildings have you seen in your neighbourhood? I have seen plenty of these buildings in many countries, some buildings without renovation and some after complete renovation. But I often wonder what happens to the indoor environment if the building envelope is insulated and airtight and the heating system is under control? Would natural ventilation provide good indoor environment and controlled thermal comfort, even though humans are not really good with ventilation habits and are responsible for large differences in energy consumption in buildings?

At Healthy Buildings Conference, Hana Pustayova presented part of her research as what is the relationship between energy consumption, energy efficiency measures and the indoor environment in residential buildings?

You have seen these panel buildings built of pre-fabricated and pre-stressed concrete. These panel apartment buildings are the dominant type of residential houses built mainly in Central and Eastern Europe, but can also be found in Scandinavia and Western Europe. These buildings were built in 1980s with the external constructions made of porous concrete panels (300 mm) and windows with wooden frames with double window panes. Heating and domestic hot water are supplied by district heating system or heat exchange station. All plumbing services are led in vertical shafts and under the ceilings in the basement/ground floor. Heat is dissipated through radiators in unbalanced hydronic system.

One of these building were renovated in Slovak Republic using polystyrene insulation as wall insulation (up to 80 mm applied from outside) and mineral wool insulation for the roof, replacing windows for plastic frames windows with double glazing and sealing the building envelope. Building system was hydraulically balanced and old regulation valves were replaced with thermostatic valves with manual regulation along with post-insulating of ducts.

The practical renovation of panel buildings made in Slovakia shows that the heating consumption fell from 248,472 kWh/a to 190,733 kWh/a just after insulation of walls/roof and replacement of all windows, i.e. that resulted in savings of 23% or 34 kWh/(m2.a) respectively. Balancing the heating system and replacement of old valves for thermostatic valves with manual regulation led to further decrease of 97,638 kWh/a, i.e. leading to saving of 51% or 37 kWh/(m2.a) respectively. To sum up: before renovation the building consumed up to 106 kWh/(m2.a) which equals class D, after insulating and window replacement it was down to 72 kWh/(m2.a) which corresponds to class C and after complex renovation with balancing the system it was class B according Energy Performance of Buildings classification.

The simulation of the fluctuation of indoor temperature in software based on real data showed that before the renovation the mean air temperature fluctuated from 21.0-25.5°C and the operative temperature fluctuated from 21.0-25.0°C. After application of insulation and windows replacement, the mean air and operative temperatures had increased almost up to 25.0°C as the inhabitants had no control of the unbalanced hydronic system. After balancing the system and valve replacement, the mean and operative temperature became stable and for most of the year it remains between 21.0-21.5°C with a fluctuation of temperatures during the summer months (May to September from 21.5-24.5°C due to possible overheating caused by sun).

The evaluation of thermal environment was performed using PMV (predicted mean vote) and PPD (predicted percentage of dissatisfied people) indices. Before the renovation people were finding the thermal environment as slightly warm or neutral. After insulation and window replacement, the inhabitants were clearly satisfied with having more warm or neutral environment. After balancing the system, the residents preferred thermal sensation between slightly warm and warm (PMV = 1.45).

This article is part of the series about the Environmental program in Sweden (Miljöprogram i Sverige).

Photo by Hana Pustayova