Ventilation system improves indoor climate

Anne Berit Bjørken

The families who live in the new energy efficient housing estate at Bromstad in Trondheim are very pleased with the air quality in their detached houses. The ventilation system that was installed when the houses were built provides a high air exchange rate.

Maren, Rolf and Randi Hoaas.

Maren Hoaas (10) has been able to cut down her use of asthma medicine since her family moved into their house at Bromstad.

"We don't know whether this is thanks to the ventilation system or to other causes, but our subjective impression is that Maren has got better," says father Rolf Hoaas.

Almost 90% of the inhabitants say that the indoor climate of the new houses is good or extremely good, and that the air is much better than it was in their previous houses.

"This confirms that a mechanical ventilation system improves the air exchange rate and helps to create a good indoor climate in domestic housing" says Hilde Nagelhus Lysne, a researcher at SINTEF Applied Thermodynamics.

"Many people feel that a good indoor climate is important. Other families have told us of children with asthma and allergies who have become much better. This has not been scientifically documented, but the subjective impressions of their parents are quite clear," says Lysne, who has been working on SINTEF's Bromstad project with Rolf Sørlie, Professor Sten Olaf Hanssen and Synnøve Frafjord.

Energy consumption

The energy consumption of the houses is somewhat higher than the estimates which were made by a firm of consultants in 1990. Nevertheless, more than half of the families say that they would still have installed a similar system today, even though it means an extra investment of NOK 25,000. (ECU 3000)

Trondheim's Bromstad "owner-builder" housing project consists of 47 detached houses with identical ventilation and energy-saving installations. The city`s owner-builder service was responsible for planning and selecting technical equipment, and for the sale of the houses. A balanced ventilation system allows users to control the quantity of filtered fresh air supply. Nowadays, balanced ventilation is quite common in office buildings, but it is still unusual to find it in domestic houses. Extract air heat pumps have also been installed in all the houses. The idea of the heat pumps is to supply sufficient heat to the ventilation air and sufficient hot water with the lowest possible energy consumption by reclaiming the waste heat in the extract air. Timers have also been installed on the housesΔ panel heaters.

Great expectations

The inhabitants had high expectations of the standard of indoor climate and energy efficiency of their new houses. The indoor climate matches their expectations to a great extent, but the average level of energy consumption is higher than the families had been given the impression to expect. "We believe that this is mainly because the original calculations were unrealistic, and that the expectations were set too high," says Lysne.

Hilde N. Lysne.

Results

The SINTEF scientists have been responsible for following up the buildings by inspecting them during the construction phase, measuring air exchange rates and temperature in certain houses, and carrying out three questionnaire surveys. They have also made detailed measurements of energy consumption for more than a year for all of the houses in the project.

The measurements show that the average energy consumption was 192 kWh/m2/year. Calculations made by SINTEF/NTH suggest that ideally, the houses can manage with 183 kWh/m2/year with only heat pumps installed, and 127 kWh/m2/year using both heat pumps and panel heater timers. "However, it is unrealistic to expect average consumption to be as low as theoretical calculations suggest, because patterns of energy use depend on the user," says Hilde Lysne. "This project has increased our awareness of the need for user-friendly systems in private houses."