draughts in dormer

sonas060

have a dormer that was built in 2003, there is crawl space under the eves that is used for storage, however when the wind in blowing in blows up into the house, there is insulation of 150mm in the eves of the roof, felt and roof slates.
any suggestions on how to stop the cold air coming into the house?
Thanks

MicktheMan

sonas060 wrote: »

any suggestions on how to stop the cold air coming into the house?
Thanks

If you want to continue using the space for storage, the best way is to convert the roof from a cold roof to a warm roof incorporating a proper airtightness barrier.

sonas060

how do I go about incorperating an airtight barrier into the roof?
Thanks

goat2

i am also interested in this, as i also live in a dormer, and i find that the crawl space is quiet draughty, i intend doing something about,

MicktheMan

sonas060 wrote: »

how do I go about incorperating an airtight barrier into the roof?
Thanks

Depends on current roof structure but my preferred method is to do it from the outside.
Best to talk to an architect who can assess your roof structure, & draw up specifications, junction detailing etc.

goat2

i intend doing it from the inside, what are the different kinds of insulation available, i am looking for stuff for the triangle crawl space at the sides of upstairs bedrooms so we will have to cut into the plasterboard to get to them

BryanF

i dealing with this at the moment, quotes are varying quiet a bit and I'm having trouble explaining to builders calling themselves 'air-tightness installers' why sticking up superfoil sh1te or VB inside exsiting insulation is not best practice.. the only way i'm getting through to them is by saying 'if they would like to stand over this with a % of payment after a years retention, away you go, do it your way':D .. sick of these characters confusing the situation (and client) , and potentially solving a draft problem only to create a moisture problem. i'll be recommending the air-test afterwards Mick;) -well see then if they get paid the full wack..

MicktheMan

goat2 wrote: »

i intend doing it from the inside, what are the different kinds of insulation available, i am looking for stuff for the triangle crawl space at the sides of upstairs bedrooms so we will have to cut into the plasterboard to get to them

This thread is about draughts and airtightness, not insulation.
I've said it before and I'll say it again, insulation doesn't do airtightness and airtightness doesn't do insulation. Both need to be considered to achieve a decent result, this is especially true with dormers. The only way to do it correctly is to first have an understanding of the difference between the two.

MicktheMan

BryanF wrote: »

i dealing with this at the moment, quotes are varying quiet a bit and I'm having trouble explaining to builders calling themselves 'air-tightness installers' why sticking up superfoil sh1te or VB inside exsiting insulation is not best practice.. the only way i'm getting through to them is by saying 'if they would like to stand over this with a % of payment after a years retention, away you go, do it your way':D .. sick of these characters confusing the situation (and client) , and potentially solving a draft problem only to create a moisture problem. i'll be recommending the air-test afterwards Mick;) -well see then if they get paid the full wack..

I often wonder how many of these so-called "air-tightness installers" have ever witnessed a test?:D
It's funny, a few years ago these self same "builders" wouldn't give a sh1te about airtightness (shur, I've being building like this for the last 20 years!).

BryanF

Mick are you managing to convince clients to take down to plasterboard?

beyondpassive

Advising an owner of a dormer in the dublin mountains. We're advocating taking out all the linings and putting insulation board inside the rafters from wallplate to ridge and lining in airtight membrane. Its a fairly intrusive job, but piecemeal approaches just don't work, on another build we just had a carpender build insulated airtight doors for each crawlspace access hatch and insulate up the knee walls with sheepswool and chicken wire to hold it in place.

It seems every single one of the Dormers built in the country over the last 2 decades simply cannot physically be heated to comfort levels in December/January unles the heating is left on for most the day.

BryanF

its a major problem and the nature of the 'crawl' space means its hard to solve anything in there, but people don't want to know,when you suggest taking down the plasterboard to solve it..

its the joists area with drafts in under the floor that are often the hardest bit to to deal with.

MicktheMan

I find that when clients experience the blower door test they are much more informed (seeing is believing) and open to recommendations.
Because most clients still want to use their crawl space for storage combined with floor void airtightness issues I generally recommend turning the roof from cold to warm (from outside) including the a.t. membrane.
Problem is, of course, recommending suitable contractors to do the job.

goat2

beyondpassive wrote: »

Advising an owner of a dormer in the dublin mountains. We're advocating taking out all the linings and putting insulation board inside the rafters from wallplate to ridge and lining in airtight membrane. Its a fairly intrusive job, but piecemeal approaches just don't work, on another build we just had a carpender build insulated airtight doors for each crawlspace access hatch and insulate up the knee walls with sheepswool and chicken wire to hold it in place.

It seems every single one of the Dormers built in the country over the last 2 decades simply cannot physically be heated to comfort levels in December/January unles the heating is left on for most the day.

this is what i am looking at doing, thanks for the brilliant advice of this method, that crawl space is the killer, as far as i am concerned, i have insulated and draught proofed the rest of home to the hilth, but i know it will take alot of trouble to get in there so as you say this door will be the answer, will be getting on with it in january,

goat2

BryanF wrote: »

its a major problem and the nature of the 'crawl' space means its hard to solve anything in there, but people don't want to know,when you suggest taking down the plasterboard to solve it..

its the joists area with drafts in under the floor that are often the hardest bit to to deal with.

how do you suggest i deal with that, as i do feel a breeze coming up through floorboards in windy weather, keeping in mind that this is going to have to be a diy job

BryanF

goat2 wrote: »

how do you suggest i deal with that, as i do feel a breeze coming up through floorboards in windy weather, keeping in mind that this is going to have to be a diy job

loads of careful air-tightness tape, I've been toying with the idea of a sprayfoam but none have a sd value, so the best i can suggest is loose dense insulation along with the the air-tightness membrane

but its convincing people to take down plasterboard to do it properly is the problem

Carlow52

In a typical dormer the floor joists run across the long axis so in most cases it is possible to get loose insulation between the joists, from the crawl space, where the kneel wall foot-plate (or sole plate) runs along the joists

Bridging pieces and recessed lights need to be considered

The attached pic of an unconverted attic may help.[ 50 feet by 30 feet ]

[Paddy147 would have a field day with foam)

In this case the joists under the photographer run along the long axis for 13 feet from the hidden gable which means no insulation can be put in, from the crawl space, after the flooring in the main section

goat2

thanks for the picture, i have a trap door onto the crawl space in the upstairs bathroom and in there i can see the joists you are speaking of, i also see a gap of about five inches of the wall to roof that is like an open window, it will be a major job, but i plan to rip off plasterboard say every twelve feet, to get in and get it six feet on either side of the openings, then i will just put up nice wood panelling to cover up the mess and paint it in with the rooms, it is great to get ideas here from people in the know and people who come up with ideas themselves

Carlow52

before u get the wrecking ball post a few pics here, there might be an easier way

howa .223

i find if theres no bridging between joists under the purlins too help act as a draft barrier this happens and as iv roofed countless dormers and bridge between joist under the purlin stud it helps stop drafts between living space and the crawl space plus your crawl hatch doors how are these sealed? but you still need air thightness barrier done properly too achieve a good seal. would really need too see photos

BrenCooney

Hi Sonas060,

I had the same problem for the past 5 years after moving to the "sunny south east". They just dont mention the wind you experience when you live 300 metres from the sea!
I had enough last winter with the drafts, which i used to feel blowing from the wall sockets and the thought of all that warm air just blowing out within 15 minutes drove me to distraction.
So i got a neighbour who is also a builder to do something for me. That he has won awards in europe for his timber frame passive house building standards helped! PM me if you want his details as he has built timber framed passive houses as far away as kerry, sligo and dublin.

1. First pic shows the detail of how he provided for the airtightness along the outside walls. you can see the "mastic" and the vapour block membrane being stuck to it and to a fillet of wood he installed along the wall plate.


2. Second pic shows how the vapour block is lapped over the existing rafters and how it is taped airtight. The stainless steel tube is from the kitchen extractor. The existing rafters were 125mm.


3. The third pic shows how the rafters were then built up to give a total depth of 250mm. i decided that if i was going to make the roof airtight then i might as well increase the insulation.


4. The fourth pic shows roof with the insulation going on. I used common mineral wool insulation. The red sheet on top was radon barrier which was used to cover the roof every night to keep off the rain. The house was cool during the retro fit as this was during MArch and April earlier this year.



5. This pic shows the back of the house and you can see the dormers, velux windows openings and 9mm OSB boards in place with the blue vapour permable layer installed on counter battons and the tiling battons holding it down. The OSB boards were taped as well. Intresting fact. As the roof was increased in depth we had to get new dormer windows and the open space was smaller. We got Munster Joinery triple glaze and are happy with the windows. The installers were however another story. PM for details.




We are heating the house at the moment using a 5 kw insert stove, and leaving open the doors for hot air circulation.
I am very pleased with the result especially as we have elimated all drafts and the air temperature is very stable and the house keeps its heat along time.

This was not cheap but given the comfort and the reduction in heating was well worth it.

Fingers crossed as this is the first time i put pics in a reply!
BrenC.

BrenCooney

Two more pics showing the taping of the OSB boards and a view into the roof.





BrenC

sonas060

Thanks for the replies so far,
Bren you solution looks to be the best, pictures of the work are very informative, however not in a position to undertake that scale of work at the moment,
looking for a solution to lessen the problem without have to take down plasterboard or take off the roof.

BryanF

sonas060 wrote: »

Thanks for the replies so far,
Bren you solution looks to be the best, pictures of the work are very informative, however not in a position to undertake that scale of work at the moment,
looking for a solution to lessen the problem without have to take down plasterboard or take off the roof.

this is the problem many face..

BrenCooney

Hi Sonas060,
I tried many other methods of trying to seal the drafts, spray foam from cans, fibre glass, "kingspan" sheets glued to joists, PE sheeting tacked to wall studs along the crawl space, and after having spent many hundreds and no closer to stopping the wind howling through the house i had to admit defeat.
thats why i invested in the full roof job.

good luck with what you try!

brenc

Carlow52

BrenCooney wrote: »

Hi Sonas060,
I tried many other methods of trying to seal the drafts, spray foam from cans, fibre glass, "kingspan" sheets glued to joists, PE sheeting tacked to wall studs along the crawl space, and after having spent many hundreds and no closer to stopping the wind howling through the house i had to admit defeat.
thats why i invested in the full roof job.

good luck with what you try!

brenc

The logic is a bit like trying to stop sound permeating your space.
You try all the different sub-optimal options and then the only solution is stop it at source, in Brens case stop it at the point of entry.

In passing, have u the doors and windows shuttered?

howa .223

have you any finish pics of eves with soffit fasia gutters etc @ brenc
thanks

beyondpassive

BrenCooney wrote: »

thats why i invested in the full roof job.
brenc

Thats the nub of the issue, well stated.

A piecemeal approach simply doesn't work, you really do have to tackle it comprehensively. I've seen a few upgrades where a piecemeal approach was adopted, but like going into Tesco only for a carton of milk and coming out with a full trolley, once you start works on a dormer, it difficult to know where to stop and before very long you're spending money you don't have.

mickdw

What is the best material from a tube/can for filling obvious holes?

We learned before on a large commercial job that expanding foam proved to be about as airtight as a sieve. This was in the days before air tightness regs but pressure test was required in a raised floor area to ensure fire compartmentation. We found fire foam had close to zero effect on air movement. The whole area had to be redone with a fire mastic from a gun.

BrenCooney

hi Howa .223

Attached is a pic of the side of the house.


I didnt replace the facia and soffit with the usual white pvc, but covered the structure with Douglas Fir 4" t&g for the soffit and a combination 9" and 7" planks for the facia.

cost prevented me from getting galvinised or even copper gutters (10 times the difference) so i went with a low key round black pvc gutter and downpipe. it actually looks not bad against the wood. the facia on the front and back were cut at an angle as you can see clearly on the RHS facia.

BrenC

goat2

BrenCooney wrote: »

Hi Sonas060,
I tried many other methods of trying to seal the drafts, spray foam from cans, fibre glass, "kingspan" sheets glued to joists, PE sheeting tacked to wall studs along the crawl space, and after having spent many hundreds and no closer to stopping the wind howling through the house i had to admit defeat.
thats why i invested in the full roof job.

good luck with what you try!

brenc

you mention fiberglass, does that get soggy if it gets damp

mickdw

Brencooney,

The air tightness looks a brilliant job but the new build up looks to have added significant loads to the roof surface. What type of roof structure do you have and did you have to alter the structure internally in anyway to carry the new setup?

BrenCooney

Hi mickdw,

The lads i got in to do the renovation had a look at the existing roof and agreed that the existing purlins and roof structure were fairly substantial and would carry the additional load. They had a good poke in the crawl space abd could see that while the original builder had a very poor idea of insulation, finese, and general good building techinques, compensated by overengineering the timber construction of the roof. This would not be true in other cases.


dont understand your question goat2. why would it get damp?


brenc