Outside Jack Frost is bundled up and the line on the bottom of the thermometer can barely be seen. How is it, then, to live in a house that is heated by body heat and by the electrical appliances in the house?
We asked a few tenants and managers of passive houses how they experience the hard cold. Have they turned ice blue?

In the row house area Lindås south of Göteborg, Sweden's 20 first passive houses were built. Marianne and Per-Gunnar Amgarth were among the first to move in in 2001, so they have experienced many cold spells.
- It was very cold a few times before, but not like this year, says Marianne when she shows us into the cottage-like warmth.
Two small radiators are connected to their heat exchanger as a reserve if the self-generate heat, in spite of it all, isn't enough.
- We have seldom had a need to use the radiators, but this winter we have actually had to use at least one on a couple of occasions. But that was only necessary for a short while till and it was quickly warm and pleasant in the entire house, explains, Marianne.
The electrical radiator is a 900 W (something like that of a toaster) and is connected to the household electrical system.

Marianne and Per-Gunnar Amgarth have lived in a passive house in Lindås south of Göteborg for 9 years and are very satisfied. During the winter's hard cold they have occasionally used the two small heating radiators that are connected to the heat exchanger to maintain a pleasant inside temperature, but, in general, the system has taken care of itself. Photo: Kristin Fridholm

Pleasant all year

The row houses in Lindås are 120 sq m each split onto two levels. The entrance is glassed in that hinders drafts and on the roof there is a 5 sq m surface with solar panels. The solar panels cover about 40 percent of the tap water heating. The thick walls and the small boxes for ventilating the air in the room on the second floor provide further visual proof that the houses really are energy efficient. Otherwise they look like any other house.

- On a normal day we don't think about the passive house technology, says Per-Gunnar. Heat exchangers and its related parts are esthetically built into the walls and not seen. The air in here is always pleasant and perfectly comfortable all year, we feel.
- What we have noticed is the lower energy cost. adds Marianne. Previously we lived in an older house not far from here and it cost quite a bit to warm up in the winter.

Control measurements in the cold

Ida Hammar and Anders Aronsson live with their two children in the residential area of Östra Tjuvsundsberget in Kungshamn. There flat lies high up on Sotenäsets south-most cape and the view towards the sea is fantastic. But the location makes it quite vulnerable to the forces of the weather.
-Here, so close to the seas gusts there could easily and often be draughty and bothersome during the winter, but we haven't felt that at all, says Ida. We have actually wondered how it could be so comfortable indoors compared with previous flats we have lived in.

The 16 rental flats stood ready for move-in February 2009 and after a short setting in period the ventilations system has functioned essentially problem-free.

Supplements of heating in the winter are produced by ground-source heat electricity. Every section of four flats is equipped with a ground-source heating pump and all heating is included in the rent.

- The system has worked very well even now in the cold, says Helene Stranne managing director at Bostadsbolaget (the municipal housing office) at Sotenäs Housing. We have been out and control-measured the indoor temperatures in the flats and they have been at an average of 22 degrees.

Shared heating

Hans Eek is the architect and consultant at the Passive House center and he has many years experience with energy-saving houses. Hans experience with the cold winters has been that residents of flats and row houses, where several units share the same ventilation system, have not had any real problems maintaining the heat even on the coldest days. This can be a little more difficult, however, in a free-standing building.

- I have had contact with a person who had spent relatively little time in his home and who seldom cooks or does anything else that produces heat and then it was evidently been difficult to get the heat up to a comfortable temperature in the house. In this house it was necessary to supplement with an external heating fan during some periods. In another case, a house-owner suffered from ice build-up in the suction parts of the heat exchanger and was forced to remove it manually, but, in general I have only been met with satisfied homeowners and tenants, he explains.

A fine-tuned system

The fact that the heating that is produced inside a passive house is actually taken advantage of is something that Fredrik Gustafsson and Caroline Nordstrand in Göteborg have experienced. They live in a two-room flat in Hamnhuset on Hisingen.
- Sometimes we have noticed that it has been a little cool in the flat in the mornings when we hadn't been up and about for several hours. But it is enough to start cooking or vacuuming to get us to the point of needing to remove extra layers because it quickly gets warm, says, Fredrik.

The possibility to raise the temperature via the flatås extra electrically-driven heating battery (in addition to the remote heating that the common system is connected to) has never been made use of.

This is the second winter that Hamnhus residents have lived in their new flats and now the system is really showing what it can do.

“ We have done measurements that show that we, during November and December 2009, decreased the building's heat energy consumption by 45 percent compared with 2008, says Per Andersson, project manager at Älvstranden Development.

Now our measurements indicate that our average consumption of 61kWh per sq meter and year and we are satisfied with that. The goal from the beginning was 60 kWh per sq meter and year and normally it takes one to three years to reach the optimal operation levels.