Help on insulation in extension please!!!!!

2 years ago

Living in the UK. We had a single story extension off the back of our house and it was completed last year. We got through this winter but noticed that it was difficult to get the space warm - even when we had the heating on for over an hour in the morning before using it.

The extension is high up as our house is on a slope so the floor is suspended with a void underneath. The void is accessible but we have put a well insulated door over the entrance to the crawl space to help keep it warm. Because we are using the space for storage, there is fire board finishing the underside. We have removed some of this and noticed a few gaps in the cellotex that is battened between the joists and so have filled with expanding foam.

When trouble shooting why it does not stay warm, I removed the front of a plug socket and noticed that there was a significant draft coming from the hole where the electric cable was in the cellotex. After getting up the original plans, I have noticed that although there is cellotex inbetween the studs, there should have been an additional layer of 25mm insulation on top of the stud work before the plasterboard was put on. The project is now finished and kitchen in in etc.

We have contacted our builder (who is actually quite reasonable) and are due to have a meeting with him this month to try and remedy a solution. I would appreciate some advice as to what we can do retrospectively that will do something to make up for the missing layer of insulation. We have used a small amount of fire grade expanding foam to seal the gaps around the electrical boxes to stop the initial drafts that we found taking off the face plate. But we would like to meet with our builder with some level of knowledge of what could be done to sort this and improve the warmth factor.

The original build was meant to be timber frame, but was changed to brick for various reasons (I'll not go into detail here). So the construction of the walls starting externally are as follows:

Redwood cladding

Blockwork (grey)

Ventilation gap

Timber frame and studs (tied to the brick)

Cellotex style insulation between the studwork / timber frame the same depth as the wood

****missing 25mm insulation layer on top of the wooden studs / frame*****

Foil backed plasterboard

Skim

Advice / help greatly appreciated. Surely the only solution can't be to rip out kitchen and add the additional layer? 😭

Comments (5)

Jonathan
2 years ago
Are you loosing the heat upwards? Or is the radiator too small for the space? Or is your boiler struggling to heat your now larger house? Or is there alot of glass in the extension that needs consideration?
Catherine
2 years ago
Is there any chance your builder has used the plasterboard that has a layer of insulation already attached to the back of it? I know when we were building during lockdown our builder had to regularly send in photos to Building Control to demonstrate the correct amount of thermal insulation was present.
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HU-662592356
Original Author
2 years ago
No insulation on the plastierboard. And rads are fine.

Problem is drafts aeound wall cavity (you can feel it when you remove a plug face). Extra layer of insulation would have dealt with this we think? but apparebtly not needed when xhanged to using blockwork for outer wall.

Builder thinks it is draft from void underneath (floating floor) which we have access to. He thinks adding a layer of insulation to the bottom of the floor will help solve it. We dont know if block work is air tight? and if the void is a problem for the ventilation gap in the walls and air movement there.
PRO
ABAH Property Services
2 years ago
The 25mm insulation that’s been missed is a thermal bridge between timber & infill 100mm insulation. Tbh unless the infill has been badly cut you shouldn’t get much draft. Chances are ares of insulation has been missed out around sockets for easy installation as difficult to run wires and fit back boxes flush. (Unless cut out very detailed) I think the floor void will be a big part of the issue and hopefully the builder can add the insulation required to stop draft rising. Remember you’ll always need it still to vent under there to allow timber to breath.
HU-662592356
Original Author
2 years ago
So is the solution to remove the ceiling plasterboard in void, then put a 25mm layer of insulation over the floor joists underneath before putting the plasterboard back on?

just insure why building inspector didnt thibk the insulation over the walls was necessary?

Help on insulation in extension please!!!!!

Comments (5)

Jonathan

Catherine

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Help on insulation in extension please!!!!!

Comments (5)

Jonathan

Catherine

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