Due to the fact that loss of heat due to transmission is on the decrease, the loss of heat due to ventilation is becoming more important. Heat recovery units must be put into use to decrease the heat loss due to ventilation. If mechanical ventilation systems are used to create a minimum air change rate, air-tight windows are necessary - but if no ventilation grilles are used they are out of place.
States that with improved thermal insulation, ventilation heat losses are becoming increasingly important for the total heat demand of a building, particularly multistorey buildings. Explains how the ventilation heat loss of individual rooms
The air exchange rate and total heat loss were measured in 11 detached dwellings to find the relationship between measured and calculated transmission heat loss factors based on standard Norwegian calculation methods. For 9 houses the measurements were done under stable climatic conditions. Air change rate varied between 0.2 and 0.7 ach with an average value of 0.45 ach. These measurements, together with several others, confirm that the Norwegian Standard (NS3031) for calculation of the transmission heat losses is reasonably correct.
The interaction of air leakage and transmission heat through a double frame window makes the overall heat loss less than the sum of them acting separately. Theoretical calculation shows that in the case of infiltration, a double frame window may recover 21% to 32% of air leakage heat loss, and exfiltrated air through a double frame window not only loses no energy but, on the contrary, reduces the energy consumption of heat transmission, covering 23% to 36% of the enthalpy drop of exfiltrated air before and after leakage. Experimental data and field test agreed well with these results.
This paper examines the excess ventilation losses arising from window opening behaviour by occupants and using data from a number of sources relates these losses to the outside air temperature. These excess ventilation losses alter the shape of the total heat loss predictions and bring these more into line with the energy consumptions measured. Excessive ventilation by open windows is shown to negate the benefits of increased fabric insulation.