New roof + Insulation approx .cost (photos included)

khards

Hi DIY experts & builders.

I know this is subjective and like asking how long is a piece of string, but I am trying to price up the potential cost of replacing a roof with slate and fitting roof insulation to a dormer bungalow.

Bungalow is around 160sqm.

The surveyor informs me that the roof will have to come off for the insulation to be fitted. Looking at the rear of the roof it looks like it is getting past it anyhow. I did wonder about spray insulation through circular holes cut from the inside?

I have attached the picture of the roof below. Thanks for any help you may be able to give.

BryanF

Don't forget an air-tightness membrane

paddy147

You will need vent cards on the inside to do spray foam (Bio-Foam 800 open cell).

Only way to spray foam is to take down ceilings and start from scratch.

khards

Thanks for the information on spray insulation. From the report I have received they say in order to comply with current building regs that the house will have to be fitted out with insulation between the rafters.

Lots to think about with this project...

Outkast_IRE

its not a big deal , its actually the normal way they do it in germany, im just back from a course in germany which went through passive housing and retrofiting to this standard.
Now i know your not trying to achieve passive standard but they do have great knowledge in insulating roofs.

Whats also considered there is the phase change, basically if its a really sunny day how long before that heat makes it through the insulation and turn the attic room into a furnace
Wood fibre based insulations are much better at this than glass fibre etc, and can make a big difference to the comfort factor.

If you want i can pm you with the address of a brochure which gives an overview of the advantages of wood fibre based insulations.

As previously metioned dont forget the wind tightness layer on the outside which should be taped , this membrane should be highly diffusible just ensure the right one is used.

Im personally not a fan of the biofoam anymore but i do understand its merits.

khards

For anyone else interested in reading about air tightness layers (I had never heard of it before) there is a page of information here

Outkast_IRE

just a word of warning though , if your going to try and go airtight do it right, if done half arsed it can lead to lots of moisture getting trapped in behind the gaps which will lead to mould and possible rot in timber.

If done right its helps alot.

Outkast_IRE

khards wrote: »

For anyone else interested in reading about air tightness layers (I had never heard of it before) there is a page of information here

Also concerning the roof and other areas, there can be an outer windtightness layer which is easily diffusible and an inside air tightness layer which is still diffusible but not as easily. the SD values are on the membranes for this purpose.