Loft insulation

7 Jan 2011
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United Kingdom
I'm thinking of building a warm room in my loft, to protect what's stored up there, and the boiler that was installed there by previous owners.

We have a hipped, cut roof (I think? Original 1930s, so not trussed)

Was thinking of rafter insulation down to purlin, then verticle walls down. Celotex or similar in rafters, slabbed mineral wool in walls, rolled wool in eaves.

Do I need to cover/clad the celotex in plasterboard? Is there something lighter I can use? Roof has already been re roofed in concrete tiles (again previous owners) with no sign of BCO sign off, so worried about weight.

Nothing but storage and boiler, just got things stored that wouldn't like getting too cold
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That wont be making a warm room. It will make an insulated cold room. And may even be making an insulated cold room with condensation issues.
We've got vent tiles installed, so hopefully condensation wouldn't be an issue in the eaves.

In the room, ventilation would be required for the boiler regardless, so I'd put the required vents in.

Would the heat from below not warm the room? There is no insulation in the floor/joists
No, the heat loss will be greater than the heat input so the room will match the temperature of the outside ambient air.

It's not about ventilation in the eaves. You may well have a vent for a boiler, but you wont have cross ventilation, and by the very process of trying to insulate you will be preventing ventilation as ( I suspect in your mind) that will make the room cold!

And this warm air which you know is getting up there, will need to deposit its moisture somewhere when it cools
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All good points woody, and why I asked here before I did anything.

I'm not too worried about how cold the room gets, as long as its higher than outside. As I say, it's just for storage, so plenty of ventilation wouldn't be an issue.

Plan B is let the boiler use its anti freeze function, and use sealed boxes for storage and standard loft roll/legs to get the boarding

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