Thermal separation between garage and house

Hello everyone,

I am currently planning a single-family house, basement included, with a garage. The thermal envelope includes the house and the basement. The garage is directly adjacent to the house and is to be fully basemented. My question at this point: How can a thermal separation be best achieved here without constructing two separate buildings? My first thought was to thermally decouple the floor slab and the two ceilings via XPS and to connect them with stainless steel (e.g., stainless steel) (similar to iso baskets) to avoid settlements.

What is your opinion? How would this be technically best realized? I would be very grateful for constructive help!

Best regards

I also pondered over it for a long time, but the simplest, cleanest options are:

[*]You include the garage completely within the building’s thermal envelope [*]You separate the two parts completely, without any (rigid) connection

We decided on option 2 – I was also “afraid” of settlements, but so far nothing of that is visible (I don’t expect any either – but of course that also depends on your soil conditions). The tricky part is the sealing (for components in contact with the ground), because you don’t want water in between – in our case, this was solved by embedding joint tapes into the slab and walls, creating a continuous barrier. However, this must also be carried on the upper side, meaning a clean sealing of the transition in the roof area. Theoretically, you could also use EPS or PUR between the two building bodies to possibly reduce the necessary insulation thickness, but it must be sealed meticulously during the construction phase, otherwise water will find its way in. That’s why I opted for XPS.

Although, in your case it might also be worth considering including the basement part of the garage in the thermal envelope and constructing the ceiling (if height-wise possible) with XPS boards as formwork for the garage floor slab.

The problems with the sealing remain the same, but you wouldn't have any concerns regarding settlements at all, because the garage would still ultimately rest on the main foundation.

The stairs, however, make it difficult again...

Do your neighbors already know about their luck because you are digging around on their property for several meters?

Although, in your case it might also be worth considering to include the basement part of the garage in the thermal envelope and to execute the ceiling (if height-wise possible) with XPS boards as formwork for the garage floor slab.

The problems with the sealing remain more or less the same, but you wouldn’t have any worries regarding settlements at all, because the garage would ultimately still rest on the main foundation.

The stairs, however, make it difficult again...

That's exactly what I was thinking as well, but as you said, it's a problem with the stairs... Do you have any experience regarding the thermal separation using XPS?

That's exactly what I was thinking too, but as you said, it's a problem with the stairs...

In my opinion, it depends on whether you want to use it as a garage cellar or rather as a house cellar with an additional access to the garage. If you expect to move things back and forth between the garage and garage cellar repeatedly, then a door between them doesn't make sense, it's actually quite inconvenient. In that case, it's better to consider house and house cellar and garage and garage cellar as two separate units.

Otherwise, the "staircase" can also be insulated. It's a bit fiddly, and you have to watch out for all sorts of thermal bridges, but it's not uncommon either.

However, it would also be important to clarify the fire protection regulations – depending on the federal state, it is quite possible that you have to equip all connections to the house with fire doors. Also consider the supply shafts/openings; for such constructions (wall-insulation-wall) there are fewer ready-made solutions and some tinkering is required – depending on fire protection requirements, you might need to consult specialists.

Do you have any experience regarding the thermal separation using XPS?

What exactly do you want to know? As an "intermediate wall" solution it works perfectly – at least with precast concrete parts they implemented everything almost down to the millimeter. As formwork/insulation for the floor slab, it has become the standard anyway.

You should definitely look at the door jambs in the detailed planning and make sure there is enough space to insulate them accordingly, otherwise you might have potential thermal bridges there.