Tag Archives: Thermal Bridge Detail

Window/Door Thermal Bridge Detail

Installation Detail

Below is the plan to deal with the window/door threshold detail to minimise thermal bridging and provide airtightness.

The window sits on a 30mm piece of Compacfoam . I used Compacfoam 200. I rebated the Compacfoam under the window so that the floor boards would fit under the window and sit on the non rebated edge.

frame mounted on compacfoam with a routed rebate
Compacfoam 30mm with rebate (Used router to rebate)

I placed 15mm Compacfoam along the lenght of the window and glued these with Orcon F.  The direction of the Compacfoam will determine the floor board direction.

compacfoam
Strips of Compacfoam

I then used 15mm Aerogel to seal around the Compacfoam. Under the window I installed the Proclima profil tape so that I could tape the Intello membrane later.

I left the centre protection tape in place on the Intello profil so that the wooden floor would go in as far as possible on the membrane.

aerogel
Aerogel 15mm

The Intello membrane was then taped ensuring that it was placed as near to the window as possible .  I taped the membrane to the floor . This finished the detail.

proclima
Proclima Solitex Plus in place

An example of the possible future wooden floor sample in place is seen below or stone/slate or marble finish.

floor board

I will first seal the floor with a product from Lakeland paint in the UK in order to minimise dust. (It looks like a very high eco specification sealer ).

I then plan to install a marble /stone slab to bridge the gap and connect this to the wooden floor.

 

 

Thermal Bridges

As part of the passive house requirement one needs to eliminate or minimise heat loss through linear lengths or points around the house. Some of the thermal bridges in my build are typical of other builds. I hope to provide more details in the future.

One of the main linear heat losses is with window/door installations (its connection with the wall frame ). It has been said numerous times that selecting a high quality window/door and installing it poorly can equate to buying a low energy window .

As mentioned before I will use the free software called Therm to calculate the losses. The first detail to tackle is the glazing which was directly mounted in the frame of the house without a window frame.  These windows are 2.4 metres x .9 metre and there are 11 of these mounted on the south face.

The calculation of these linear losses can be expensive to get done so I will be doing the task myself and have it checked by others. I am surprised that good details are hard to come by on the web for free to help the self builder. One of the most time consuming exercises with thermal bridge calculations is drawing the detail. If one undertakes drawing this oneself using CAD (Computer Aided Design) software it can help to reduce the cost of the calculation.

When one needs to come up with a detail to minimise the losses there are a lot of products that help to keep the losses under control. These are semi-rigid insulation products like compacfoam, foamglass blocks, standard insulation, TECTEM, PU or rockwool and fibreglass products and aerogels (which is one of the highest performing insulators being made).

To date there appears to be very few online resources to guide the self builder or provide details that one can use before one starts a build.

Some background and details I found to date on thermal bridges can be found at the following links.

What is a Thermal Bridge

Leeds Beckett University

Scottish Thermal Bridge Details Link

Example of Heat Loss through a glass spacer

Below is an example of the thermal bridge calculations one needs to carry out to establish the thermal bridge performance values in W/(mk).

  • One draws the detail as a DXF file using a drawing package (or draw the detail manually in Therm)
  • Import the detail into Therm Software
  • Add the technical details such as thermal conductivity of each item
  • Tell Therm where on the drawing to stop the calculation (Adiabatic)-top and bottom of the drawing shown below.
  • Tell Therm what the internal and external temperatures are
  • Go to a spreadsheet and calculate the psi values of the thermal bridge detail for the passive house performance value.

When this is done one ends up with the calculation and an image like that shown below. In this image the glass is shown near the top right.

Drawing Detail

 

In the next image the colours show the temperature gradients. The purple colour is the outside temperature at -10 degrees.

colour infrared
There is thermal bridge software that one can buy where the software calculates the psi value without using a spreadsheet but Therm is free and there are courses available in Ireland.

If one wants to show the real design and installation details of the thermal bridge values for the Irish regulations rather than the accredited details (without a performance value)  one needs to use a certified thermal bridge accessors but this is not the case for the Passive House Institute.

We can all look forward to the day when standard construction details that are typically used in Ireland are already calculated for the self builder and there will be no need to pay to find out the thermal bridge losses . The Scottish accredited details (see above link) come close to taking the guess work out of construction.

 

Window Wall Build Up

Batten and Counter Batten fixing

Below are a few images of the build-up I used around the windows. The first image shows the batten (45x40mm planed ) build up on the window wall. I tried to offset the battens around the windows so as to minimse thermal bridges. The wall battens are installed at 90 degrees to the vertical window sections behind the OSB.

Passive House Timber Frame Build Up
Insulation

The image below is the RWA45 rockwook installation before the airtight membrane was installed. The wooden strips on the window sill are there to support the sill board. I kept them away from the window frame in order to decrease the thermal bridge. I now plan to use Rockwool RWA45 on all window sills as it performs better at not absorbing water as seen on a previous blog.

Window Insulation Detail Passive House
Thermal Bridge Build Up

The next image shows the finish layer of battens over the membrane.

Passive House Window Detail
Batten Finish Detail

 

 

 

 

 

 

 

 

 

 

 

The window (below) which was installed in the structural frame of the building (I purchased the glazing without the frame 2.4mx.9m) provides light and solar gain. Small lengths of floor board OSB were cut to size in order to build up the insulation and provide a base for the plasterboard finish.

wood spacers for insulation

 

 

 

 

 

 

 

 

 

 

Insulation is placed up against the glass and I plan to place a timber bead around the edge . Plasterboard will then finish the detail.

glazing insulation for glass in structure

 

 

 

 

 

 

 

 

 

 

The finished (near finished) wall looks like this below.

Passive House Wall Detail
Window Wall Detail