Is it worth insulating external house wall now inside porch?

[Anonymous]

Hi,

Sorry to ask yet another brain picking questions, but I value your collective answers more than those of my builder..or indeed most other people 😉

I'm in the middle of building a reasonably large porch. I'm viewing it as a bit of a trial run for an extension someday, as well as a significant improvement to the thermal envelope of my solid walled house. Consequently it's got 120mm of celotex in the walls and A rated d windows.

I'm now looking at the expanse of external wall now in the porch and wondering if I should ask the builder to stick on some insulated plasterboard, on the premise that it would reduce heat loss from my (generally freezing hallway) to the porch.

The general view around me is that that would be overkill and having a well insulated porch is enough. Any thoughts?

As a side issue, someone's just told me that I should have a vapour barrier in the porch. Any ideas about whether this is necessary and if so, where I should put it and how? 😉

Thanks very much for thoughts and comments,

Tania

[Nick Grant]

Tania

read this after responding to your other porch post.

Not sure what the answer is but I think you need to decide where you are putting your insulation layer. If this was new build I'd be confident advising as per my other post, see what others think.

Nick

[Anonymous]

I'd agree with Nick's response in the other thread. You need to decide where the thermal envelope lies, place the wind barrier immediately outside it & the air barrier immediately inside it.

Insulating the wall separating the house & porch creates a void part way through the thermal envelope which is occasionally ventilated to the inside, occasionally ventilated to the outside & sometimes both!

A vapour barrier in the porch can be used as the air barrier & may be necessary depending upon the wall build-up, but it won't help with the main problem which will be warm air from the house causing condensation on cold surfaces in the porch. My recommendation would be to take the porch inside the thermal envelope & get rid of the original front door.

David

[Author]

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