ᐅ Wooden Ceiling and Partial Insulation for Basement with Garage

Hello everyone,

we are planning a passive house with a timber frame structure together with an architect. The house will have a basement, with part of the basement used as a garage. We want to minimize the footprint as much as possible because the garden is very important to us. The other two rooms in the basement are intended to be used as storage space and a small workshop, possibly also for technical equipment. The basement is only expected to be heated temporarily, if at all. The kitchen will be located above the underground garage. We have discussed various options, and the garage keeps posing challenges because, of course, opening the garage door will let a rush of cold air into the house.

The architect’s proposal is to exclude the basement from the thermal envelope and build an insulated wooden ceiling above the basement to prevent thermal bridges. The ceiling is mostly above ground level and would only need to be separated from the earth with a shaft over a distance of about 5 meters (16 feet). The garage would not be insulated at all, and the rear utility rooms would only be insulated on their exterior walls. The interior wall facing the garage would of course be insulated as well. Naturally, the concrete walls would need to be properly reinforced to withstand the earth pressure.

An alternative would be to build a conventional concrete ceiling and extend the thermal envelope around the basement, but in that case the garage would need to be insulated from the inside so that we don’t get cold floors in the kitchen.

Do you have experience with wooden ceilings in lightly insulated basements? What do you think of this approach? I am concerned that different climate zones might lead to mold development.

Many thanks in advance for your help

Schwabe23 schrieb:

Thank you in advance for your help

Um... give and take: from such an interesting house, you only want to show us the driveway???

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https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/

I thought you’re not supposed to pay in advance on a construction site 🙂

Here are a few more views. We’re still refining the house and floor plan because, after calculating the costs, we’re unfortunately well over budget. We’ll be reducing about 1 meter (3 feet) on each side. Additionally, the entrance vestibule will be significantly smaller.

• With this design, the house maximizes the sunny garden area available on the plot. We want to integrate the greenery of the garden and the pond almost into the living space. At first, this will naturally have the typical showcase effect, but once it’s a bit overgrown, we imagine it will look great. Especially with the window seat in the living room.
• The house is simply something different. We didn’t want to add another plain white box to the neighborhood.
• We’re somewhat distancing ourselves from the neighbors downhill, who have a rooftop terrace on their garage (approved by the previous owner of the plot).
• We have an optimal orientation for photovoltaic panels and good solar gains in winter.
• We were always torn between an open living area and separate rooms (kitchen/dining/living). Now we see a good compromise. It’s all open yet somehow divided, with corners that aren’t visible from everywhere.
• Upstairs, under clear conditions, we have a view of the Alps.
• On the ground floor, there is a small separate apartment where a parent could potentially be cared for.

I hope someone can help me with the basement insulation. Our architect needs a decision on this. He is enthusiastic about the wooden ceiling solution, but somehow I don’t feel comfortable with that for a basement.

Best regards

I can't help you with the ceiling issue, but the design of the granny flat seems inconvenient to me. Basically, it only has one bed for sleeping. If a person in need of care can still get out of bed, they always have to walk around the house to reach the connection point. And if they can no longer get out of bed, they wouldn't want to be so isolated.

You are probably right. Since this will be a KfW 40 Plus house, the second dwelling unit must meet certain minimum requirements to qualify for the subsidy. Maybe one day a door will be installed to the main apartment if the "tenant" agrees to it...

Adding another door will further disrupt the floor plan of the secondary apartment. Whether you want to create a pseudo-living unit to qualify for higher subsidies is your decision—I don’t want to judge that. But consider that for a one-time cost of 30,000€ you will have this awkward section in the house that no one will find comfortable to live in and will likely be used only rarely. At the same time, for example, it forces you to take a staircase every time you want to go from the living room to the bathroom. If you install the door, you will have access to a bathroom on the ground floor, but it won’t even have a window, except one looking into the storage room. It’s really not very pleasant.