Insulating dormer bungalow

torrentum

Hi all,

i've asked a few perople what to do about the following and ive reveived different opinions. Hopefully someone here can help.

I live in a dormer bunglaow. The upstairs isnt developed/insulated at all, though there is planning permission for 3 rooms up there. I want to insulate before the winter comes round - but I'm unsure about how to go about it exactly.
1) Do I insulate the rafters and board the floors with insulation underneath the boards, or
2) Insulate the rafter only, and just board the floors, leaving the floors without any insulation underneath?
I was warned that insulating the floors might cause any future rooms upstairs to be cold?
Anyway, I'd be thankful if anyone can put me straight.
Many thanks.

bbam

Insulate between the rafters and then 50mm insulated slabs over that, if you insulate between and then just standard slab each rafter (~10% of the surface area) is essentially a coldbridge drawing heat from the room..
Insulate between the floor joists too, 300mm fiberglass or similar..

The dormer rooms won't be cold if they are properly insulated, reasonably airtight and of course have their own rads..

You'll never be sorry for well insulating and the "extra" it costs will be saved on heating bills...

When we built 2 years ago we were laughed at by some of the tradesmen on site for the amount of insulation used... We reduced our oil consumption by about 2.5 tanks a year which gives a saving of about €2300 a year..who's laughing now!

Price round the insulation companies, we got insulation supplied & fitted cheaper than I could buy myself...

Carlow52

Is the boarding of floor just a temp job or part of developing attic?

What is the current roof felt: is is black felt or a breathable material?

With the planning, u need to consider how much head room u will have left if u insulate between the rafters and add more insulation over them.

For max flexibility in the future I would insulate the rafters, making sure you have a breathable roof when finished and then you can work away, leave a service cavity for lights in ceiling.

IMO if u insulate floor and then convert u will have loads of issues with pipes wires etc etc

In addition if u raise level of floor 2 much u may have issues with head room and sewer pipes if ensuite upstairs

torrentum

Thank you both for the replies.

bbam

OP stated it was a dormer bungalow, I presume the height was designed in for it to be a dormer bungalow... Otherwise we'd be talking attic conversion..

Still good points on the head height...

duffman21

bbam can you pm me the details of who you got your insulation supplied & fitted from

Thanks

paddy147

I installed 100mm Kingspan board into the ceiling/roof joists of the bedrooms and then I had he ceilings slabbed out with 35mm insulated plasterbaord.

Some warmth in the house and bedrooms.

I also had the floors done for better sound and heat retention too.

Rockwool 100mm flexi slab installed 1st,and then Knauf 170mm insulation fitted ontop.

You could also spray foam the roof joists with open cell bio-foam 800.

I have both my atic spaces spray foamed,and the difference is light night and day.

duffman21

Hi paddy147

How do you find the spray foam?

Would you recommend it??? Looking into using it myself now.

Thanks

paddy147

duffman21 wrote: »

Hi paddy147

How do you find the spray foam?

Would you recommend it??? Looking into using it myself now.

Thanks

The mutts nutts.:)

exaisle

Hi Paddy147,

Can you give an idea of how much per square meter the spray foam cost?

E.

paddy147

Around 16-17 euro a square meter with the vent cards aswell.

exaisle

That sounds like a competitive price...can you PM details please?

Or if anybody can better it I'd like to hear from ya....

E

wildwest1

Hi Paddy,

Can you PM details please?
Thanks

fealeranger

Hi all I am intrested in this thread on insulating upstairs in a bunglaow. I was looking at the air-tight tape with 100mm rafter-loc between rafters, 62.5mm insulated slab over this and anywhere there is a flat surface(crawl space) is getting the 200mmX2(400mm) wool. This was advised by the BER guy trying to get a B1 rating from the house. I'm not too sure about the air-tight tape and was wondering if there is and alternative way. It does not have to super air tight but I don't want to lose heat either. I was only getting the BER to get an insulation spec Any help appreciated.

joeyoey

wildwest1 wrote: »

Hi Paddy,

Can you PM details please?
Thanks

Hi Paddy, me too if you dont mind, thanks.