In an energy-efficient building, windows play a key role in space heating through harnessing of free solar gain. This is the case with a house in Galliate built inside a barn, using FAKRO windows.
Today, it is perfectly feasible to design buildings which produce more energy than they expend, in fact with almost no energy consumption at all. Despite the absence of traditional heating they combine thermal efficiency with a comfortable living environment. By harnessing solar gain through windows, a standard calculation method set by European standards means a standard building’s energy requirement would be around 7 kW per day. By contrast, the Galliate active house was calculated to use only 2.1 kW, with minor variation subject to external ambient temperature.
It was therefore possible to develop a project with no heating system, using mechanical ventilation with heat recovery (MVHR) supported by three electrical appliances as part of sanitation facilities and a heat pump for hot water. All are powered by a photovoltaic system on the roof.
» What are the results?
“We are currently completing the performance monitoring system, but the building clearly maintains optimal conditions of comfort. This is clear from messages that the owner publishes on social media which report recorded room temperatures. Until mid-January, these never fell below 20°C and the appliances were never turned on. Performance checks have been set up by an intuitive and reliable method that also allows anyone to check whether the system meets energy consumption forecasts and expectations.”
» What role is played by windows in this low / zero heat consumption strategy?
"Even the most effective exterior doors and windows are the weakest element of a building envelope as their transmittance values are considerably higher than those of masonry. However, they also enable sunlight to pass through which provides free heat. With large areas of south-facing glazing (about 24m²) the customer chose high quality windows, including the specific FAKRO model after conducting his own online research. I then checked out how and why these products are at the top of the market for their U-value and heat loss resistance."
» BOX Excellent thermal performance
The roof windows on the house in Galliate (Novara) are the FAKRO FTT U6. It has a U-value of 0.80 W/m²K (0.71 W/m²K if installed with EHV-AT Thermo insulation). The FTT U6 is equipped with highly energy-efficient 53 mm thick, low emissivity, triple-glazing (6H-18-4HT-18-33.2T) and has the topSafe® system of anti-burglary hinge and lock reinforcement, a high pivot point and a system of five seals made using shrink-resistant HDPE.
Different sizes from the range of 12 available as standard were used, from 55x98 cm to 134x140 cm. All are made of carefully selected, close-grain pine which is vacuum-impregnated with preservative. This is the most effective method; other systems can leave even high quality timber vulnerable to the onset of mould growth. It is then finished with two coats of non-toxic acrylic lacquer.
The windows were equipped with ARZ ‘Z-Wave’ electrically operated external roller shutters to provide winter insulation. Z-wave enables windows and blinds to be operated alongside other similarly compatible appliances, in this case controlled by ZWK10 wall switches and ZWP10 multi-channel remotes.