Renovation with Internal Insulation and Heat Recovery in Real Life– Energy Savings and Risk of Mold Growth

This paper presents a pilot project for renovation of a large residential area; focus is on energy consumption and risk of mold growth. The renovation included internal insulation of walls with capillary active insulation material, balanced mechanical ventilation with heat recovery and insulation of floor towards basement. These types of measures are not completely new and have been used in other buildings as well, however the measures may be either risky regarding mold growth or the effect is uncertain with the specific external wall composition. A pilot project including six apartments was performed to test the measures in these specific buildings. Furthermore, six reference apartments were monitored simultaneously. For two years, energy use for heating was measured as well as temperature and relative humidity in the internal insulation, indoors and outside. The insulation was dismantled in two apartments after two years, to test for mold growth at the original wall surface. In extreme cases, the relative humidity in the walls behind the insulation system was up to 90 % RH shortly after installation, and mold growth models predicted growth of mold. However, the relative humidity decreased, typically to 70 % RH in the second winter. The inspection and measurements after the removal of the insulation material did not show signs of mold growth. Apparently, the used insulation material can be used in this specific case without risk of mold growth. Energy savings for heating was measured and calculated to around 25 %. However, the electricity use for ventilation was almost equal to savings from heat recovery

Testing Joints of Air and Vapour Barriers, Do We Use Relevant Testing Methods?

This article describes testing of peel and shear resistance and airtightness of joints of air and vapour barrier systems before and after artificial aging. The testing of peel and shear resistance was based on standardised methods while the test of airtightness was a method invented for this project. The results show that while peel and shear strength increased with aging, the airtightness was significantly reduced. As these two results seem to contradict each other, the methods are discussed, especially whether the standardised tests are too far from the conditions on site or joints should be tested on other materials as well. Furthermore, weaknesses in the airtightness method is also pointed out

Hygrothermal conditions in ventilated attics with different air change rates and ceiling constructions

A recently Danish study reported that no vapour barrier is needed in ceilings, if the attic is well ventilated and the ceiling towards the dwelling is airtight. Based on that study, new investigations were initiated with focus on the hygrothermal behaviour in ventilated attics with different air change rates. A test house with three sets of four different ceiling constructions – all airtight – was used in this study. The ventilation rate was reduced in two of the sets with approx. 35 % and 50 %, respectively. Air change rates were measured with tracer gas. Furthermore, temperature and relative humidity was measured every hour. Measurements in similar ceilings with mineral wool or cellulose-based insulation material show that hygroscopic properties of the insulation have very limited effect on relative humidity. Furthermore, only at low ventilation rate the effect of a vapour barrier could be measured with minor impact. Based on the short-measured period the calculations of the risk of mould growth showed no risk. The results indicate that even when the ventilation is reduced by 50 %, the ventilated attic still performs well if the ceiling is highly airtight. However, the importance of vapour barriers becomes more important at lower air change rates