The `Swedish Attic' has the ceiling to the upper floor self-supporting with a rafter roof supported by posts which rest on the upper ceiling. The system is commonly used in one and a half storey houses in which the upper floor is restricted to the area enclosed by the posts.< This study has been performed at the Royal College of Technology in Stockholm using a climate-simulator. It shows that the attic must be ventilated with continuous slots at the eaves and along the ridge.
The potential for air conditioning energy savings using exhaust fans to cool attics was investigated in six occupied townhouses at Twin Rivers. These houses were compared with similar houses without attic fans. The houses had various levels of instrumentation. Data collected for two summer months in 1977 was the basis for this study. The principal quantities measured were attic and living space temperatures, air conditioner and attic fan usage,together with outside air temperature and solar flux.
Describes technique for measuring the volume of air leaving a house through the loft. Two tracer gases are used; nitrous oxide is released in the house and carbon dioxide in the loft. The mean concentration of N2O in the loft gives the volume of house air infiltrating the loft: and the mean concentration of CO2 gives the ventilation rate of the loft itself.< Gives two examples of the use of this technique and gives loft ventilation rate as a function of wind speed for one house.
Presents mathematical model for predicting the heat transfer and moisture- transfer processes in residential attic spaces. Uses model to predict attic ventilation rates required for preventing condensation or frost accumulation on the underside of roof sheathing. Gives attic ventilation charts covering a wide range of outdoor temperatures, ceiling thermal resistances and ceiling air penetration rates. Finds that the addition of a ceiling vapour barrier reduced the required attic ventilation rate by36%, but the effectiveness of a vapour barrier was reduced by air leakage into the attic.
Calculations of water vapour flow through walls and ceilings are frequently based on the permeability of building materials and implicitly assume that most of the vapour transport takes place by diffusion. Finds that this model is generally inval
Documents and compares the air infiltration levels experienced in five Twin Rivers townhouses before and after retrofit. The retrofits sealed and caulked window frames, sealed cracks along the attic floor/party wall Junction and reduced leakage from basement to attic. Weather data and air infiltration rates were analysed using multiple regression, polar plotting, stemleaf plotting and comparisons of infiltration rates with inside to outside temperature differences. Gives results in graphs and tables.
After retrofitting of town houses at Twin Rivers it was found that heat loss from attics was much higher than predicted. This was accounted for by heat transfer within the wall dividing adjacent townhouses (party wall) from each other. This occurs both by conduction and by air movement through vertical holes in the party wall. Suggests that basement is thermally coupled to the attic and adjusts the model to allow for this, giving a three-zone model for the house