solid wall insualtion with access

[richgentry]

Hi

We've recently bought a house which has an extension to the back. This extension is single brick with a flat roof.

It currently has a stud wall construction around all four walls, covered with plasterboard. It has pipes with stopcocks and has the gas meter in one corner. It has old polystyrene insulation. It has a concrete floor.

We want to insulate it properly.

From reading so far it appears we want to remove the old plasterboard, fill the studwork with Celotex style insulation, then a vapour barrier, then plasterboard, then skim. At the same time we need a DPC on the floor before any floor insulation.

We will put insulation above in the future to have a warm flat roof construction when the roof needs doing. What's the best thing to do in the meantime. Just put a vapour barrier in but no insulation?

Also we need access to the stopcocks and gas meter. How do we keep this access and insulate the room properly?



Many thanks for any replies.

 

[SmileyDan]

What do you mean by "insulate it properly"? What U values are you attempting to achieve? What is your goal?

What you have described won't be as thermally efficient as is possible because you are simply filling studwork. Heat conducts through studwork. The most thermally efficient, normally, is to insulate externally. This also has the benefit of making your existing brick wall act as a thermal store to regulate temperature.

If you are really interested in thermal efficiency then you may find some of the "green building" forums more useful although note this gets very detailed.

 

[richgentry]

Hi

Cheers for the response

By properly I mean to do a decent job that will give a warm room in winter and not lead to issues with damp etc down the line.

Insulating externally is impractical as the roof doesn't overhang far enough. Also one wall joins a neighbor's extension. However as the neighbours extension is completely insulated with a clear plastic roof we'd like to insulate that wall as well.

 

[JohnD]

Internal insulation behind the plasterboard as you describe will do a very satisfactory job. Thermal conductivity of wooden studwork is not very high.

You might consider using an insulating plasterboard when you finish off, which will add slightly to overall efficiency, and reduce risk of dust shadows showing the studs on the decorated wall.

If you have an uninsulated flat roof, then heat loss through the ceiling will be very bad. You might consider pulling down the ceiling plasterboard while you are doing the walls.

 

[SmileyDan]

From what you describe, your current approach will be fine. You need to sort the roof out obviously. And it sounds like a good time to max up on floor insulation. Don't feel tempted to put downlighters in the ceiling.

 

[richgentry]

Totally open to pulling down the ceiling plasterboard,

Just not sure whether to insulate from the inside or outside due to reading that it should be done from the outside with flat roofs due to condensation.

Also not sure what to do about providing access to stopcocks. I can build access doors but they would obviously allow damp air into the cavity behind the studwork.

 

[JohnD]

I'm not sure about flat roofs. Ask on the Roofing section. There may be a way to ventilate to outside air the gap above the insulation and below the deck.

For the stopcocks, perhaps you could line the enclosure with the Celotex that has a foil membrane covering, and tape the joints to prevent water vapour getting through. It may have to be quite thin.