Insulating a period property

[trell]

Hi all

New post here, and please bear with me, I'm not much good with forums, DIY & whatnot....

My dilemma is that I have an old period property that I want to insulate. My first consideration is the sloping roof.

The attic area itself is a large area, designed as a walk-in space (The stairs lead right up and there is no need for ladders etc for access), so assuming that I do this right, it has the potential for a loft conversion. Being a period property though, I would like to keep the joists exposed, as this is part of the charm of the building.


The problems start, however with the fact that the joists in the roof are only 80mm thick, and, being a period property, I have to be very careful with the material that I actually use. Based on what I have read, I have to leave approx. 50mm ventilation in order to prevent condensation. This gives me only 30mm to play with, and even less if I want to keep the joists exposed.

So basically, I'm asking a few questions here....What is the minimum space I can keep for ventilation? Are there any thinner alternatives for roofing insulation? and is it a viable option to keep joists exposed, or should I just cover them up?

Many thanks for any info you guys can provide.

 

[trell]

If it helps, here are some pictures of the attic....

 

[JohnD]

you could take up the floor and lay insulation under that, for a start.

I see the attic fomerly had a plastered ceiling which has been ripped out.

I see it has recently been reroofed, that would have been a good time to lay rigid boards on top of the timbers but the opportunity has been missed now

Have a look and see if that black stuff is felt or a breathable membrane

 

[datarebal]

The felt fitted is bitumen based 1f type so not breathable and probably 15 to 20 years old at a guess.
minimum gap is 50mm, plus you will have to ensure you have ventilation.
keeping the exposed rafters (being 80mm) you will not manage to get enough insulation. internally
making a big job out of it you could probably insulate externally which requires the roof covering off....
We have done this on a few buildings , a watermill and museums , pubs etc obviously with correct permissions.

A tricky situation which has been a pain in the butt for most of us and still is ..

 

[Deluks]

I'm not much good with forums, DIY & whatnot...

Then you couldn't have come to a worse place to resolve your problems


You will have to either bury the beams, fake it by building them out with reclaimed timber, or simply use less insulation and not comply with any regs.

You could probably still keep the purlin exposed in the first pic though.

Whatever happens, don't reduce the ventilation gap. Bad things could happen.


Welcome to our DIY forum, (and whatnot)