Attic Insulation Questions

Big Cheese

I am going to insulate my attic (earthwool,200mm across existing 100mm) later today but have a few small questions I hope can be answered relatively easily.

1, How close to the eaves should I go? Just enough to leave small gap for air or is there a recommended gap size?

2, Do I need to leave a gap at every single section or can you block half of the eaves and still have enough airflow?

3, Has anyone used a foil membrane tacked onto each side of sloped section of attic, above insulation?. I've seen it online but only illustrates cover small section of roof. If it is to reflect heat back into house, how effective can it be if the fibreglass stop it penetrating back to living areas?

4, Do I need to leave the section below the water tank uninsulated to allow heat transfer to tank to prevent freezing? Then just insulate all around sides and top of tank?

5, Should the extractor fan from bathroom be vented to eaves or is it harmless venting to attic space?

6, if original insulation (house built 2000) has compressed and turn a dark colour is that an indication that it is less effective and needs replacing? I'm not disposing of it but might use that stuff to insulate tank and lay some new 100mm in those areas.

7, Should I insulate water pipes even if they are going to be under earthwool or just ones above?


I have checked boards, Kinspan, Knauff, SEAI and more but still have above questions. Thanks in advanve for any input

dathi

Big Cheese wrote: »

I am going to insulate my attic (earthwool,200mm across existing 100mm) later today but have a few small questions I hope can be answered relatively easily.

1, How close to the eaves should I go? Just enough to leave small gap for air or is there a recommended gap size?

2, Do I need to leave a gap at every single section or can you block half of the eaves and still have enough airflow?

3, Has anyone used a foil membrane tacked onto each side of sloped section of attic, above insulation?. I've seen it online but only illustrates cover small section of roof. If it is to reflect heat back into house, how effective can it be if the fibreglass stop it penetrating back to living areas?

4, Do I need to leave the section below the water tank uninsulated to allow heat transfer to tank to prevent freezing? Then just insulate all around sides and top of tank?

5, Should the extractor fan from bathroom be vented to eaves or is it harmless venting to attic space?

6, if original insulation (house built 2000) has compressed and turn a dark colour is that an indication that it is less effective and needs replacing? I'm not disposing of it but might use that stuff to insulate tank and lay some new 100mm in those areas.

7, Should I insulate water pipes even if they are going to be under earthwool or just ones above?


I have checked boards, Kinspan, Knauff, SEAI and more but still have above questions. Thanks in advanve for any input

1, 50mm gap below felt
2, gap in all sections
3 complete waste of time and money
4, yes
5, should never vent into the attic must always vent to outside
6, leave in place and add new insulation on top
7, insulate all pipes even ones under insulation

Tow

dathi wrote: »

3 complete waste of time and money

I thought that until I saw/experienced it myself, it actually made a big difference to how warm the attic was in winter. Although the attic only had 100mm in it before hand. So may be a waste if in addition too 300mm of rockwool, and it does not come cheep.

Calibos

Foil across the rafters/roof trusses as opposed to the ceiling joists is useless unless you need a warm attic. More use in Summer actually where it keeps attic cooler by reflecting radiant heat back at the slates.

If your bathroom extractor has been venting into attic instead of through roof to outside since 2000 I'd worry the dark insulation is actually a sign of mold?? In which case it should be removed completely and extractor venting prioritised ASAP.

I defer to daithi's expertise.

dathi

Tow wrote: »

I thought that until I saw/experienced it myself, it actually made a big difference to how warm the attic was in winter. Although the attic only had 100mm in it before hand. So may be a waste if in addition too 300mm of rockwool, and it does not come cheep.

by placing the foil on the rafters you have cut down the amount of air circulating in your attic and this is what you are feeling as an improvement in temp.(any plastic would cut down air movement in this way) the problem with placing the foil where you have is that any moisture generated in the house that migrates through the plaster board layer (as most irish homes did not have a vapour control layer placed between plaster board and insulation) has no means of escape. as you have blocked of the cross ventilation of the attic which is used to disapate this moisture, and so the moisture will condense in the attic . which can lead to mold and structural damage to timbers

Big Cheese

dathi wrote:

1, 50mm gap below felt 2, gap in all sections 3 complete waste of time and money 4, yes 5, should never vent into the attic must always vent to outside 6, leave in place and add new insulation on top 7, insulate all pipes even ones under insulation

Cheers for the advice, to the point.

Big Cheese

Tow wrote:

I thought that until I saw/experienced it myself, it actually made a big difference to how warm the attic was in winter. Although the attic only had 100mm in it before hand. So may be a waste if in addition too 300mm of rockwool, and it does not come cheep.

I think I might give the foil a miss, not convinced of it fully

Big Cheese

Calibos wrote:

If your bathroom extractor has been venting into attic instead of through roof to outside since 2000 I'd worry the dark insulation is actually a sign of mold?? In which case it should be removed completely and extractor venting prioritised ASAP.

There is one extractor fan that is vented to the eaves, in the en suite. However, the main bathroom had no vent other than hole in the wall. So up to now there has been no extracting into attic. But will double check its not mould. Cheers

normanbond

Can anyone help/advise me?
I have an open access to the attic bedroom via staircase. There is no door to attic, just a wooden staircase.
There is serious heat loss during the winter.
At the top of the staircase is a rectangular banister. I'm looking for insulation ideas for this banister area.

It measures approx 14' x 5' and 3.5' high.

Is there any kind of lagging jacket that could be got for this or any insulation ideas????

cerastes

dathi wrote: »

by placing the foil on the rafters you have cut down the amount of air circulating in your attic and this is what you are feeling as an improvement in temp.(any plastic would cut down air movement in this way) the problem with placing the foil where you have is that any moisture generated in the house that migrates through the plaster board layer (as most irish homes did not have a vapour control layer placed between plaster board and insulation) has no means of escape. as you have blocked of the cross ventilation of the attic which is used to disapate this moisture, and so the moisture will condense in the attic . which can lead to mold and structural damage to timbers

If an attic is converted and the existing top side of the ceiling and the new flooring covered, wouldnt this mean that moisture may get trapped in the ceiling/new floor of the attic?
If a vapour layer is placed over the top surface of beams and plasterboard ceiling, wouldnt this mean that moisture may get trapped in the now enclosed existing ceiling/new floor beams, causing mould?
Doesnt a foil barrier prevent the same thing?

dathi

cerastes wrote: »

If an attic is converted and the existing top side of the ceiling and the new flooring covered, wouldnt this mean that moisture may get trapped in the ceiling/new floor of the attic?
If a vapour layer is placed over the top surface of beams and plasterboard ceiling, wouldnt this mean that moisture may get trapped in the now enclosed existing ceiling/new floor beams, causing mould?
Doesnt a foil barrier prevent the same thing?

if the attic is converted then the insulation in the attic floor remains warm as it is inside the heated zone so condensation will not form.

vapor layer must be placed on warm side of insulation ie. between the plaster board and the bottom of the joists not on top of the joists.

cerastes

dathi wrote: »

if the attic is converted then the insulation in the attic floor remains warm as it is inside the heated zone so condensation will not form.

vapor layer must be placed on warm side of insulation ie. between the plaster board and the bottom of the joists not on top of the joists.

I thought a breathable membrane could go or had to go on the cold side, so that moisture from outside couldnt get through but any moisture inside would still be able to work its way out, (in the case of say a very small but unoticed drip or leak from the existing roof structure, or from any condensation that might drip down from the felt) so it couldnt transfer through joints or sit on the cold side of the new insulation.

I can see a non-permeable membrane would be needed on the inside of the plasterboard to prevent the transfer of moisture laden warmer air into the roof structure.

BUT
In my post I meant, if the attic is newly converted, how is the existing ceiling of the upstairs dealt with? warm moist air may leak into holes/gaps and spaces in the ceiling and may make its way into the space between the ceiling and the now converted attic floor, get trapped there and cause dampness? or create a condition for mould.
Even if you seal the joists with a vapour control membrane, the ceiling joists will be exposed to potential damp/mould?
Even If there is no ingress of moisture to the space between the upstairs ceiling and a newly converted attic, can other forms of dry rot set in due to no ventilation of the space?

The only way I can think around this is, which Ive read is acceptable but am not certain, that if the ceiling is foil backed, this acts as a vapour control layer, just that any holes around light fittings need to be sealed up properly.

dathi

cerastes wrote: »

I thought a breathable membrane could go or had to go on the cold side, so that moisture from outside couldnt get through but any moisture inside would still be able to work its way out, (in the case of say a very small but unoticed drip or leak from the existing roof structure, or from any condensation that might drip down from the felt) so it couldnt transfer through joints or sit on the cold side of the new insulation.

I can see a non-permeable membrane would be needed on the inside of the plasterboard to prevent the transfer of moisture laden warmer air into the roof structure.

BUT
In my post I meant, if the attic is newly converted, how is the existing ceiling of the upstairs dealt with? warm moist air may leak into holes/gaps and spaces in the ceiling and may make its way into the space between the ceiling and the now converted attic floor, get trapped there and cause dampness? or create a condition for mould.
Even if you seal the joists with a vapour control membrane, the ceiling joists will be exposed to potential damp/mould?
Even If there is no ingress of moisture to the space between the upstairs ceiling and a newly converted attic, can other forms of dry rot set in due to no ventilation of the space?

The only way I can think around this is, which Ive read is acceptable but am not certain, that if the ceiling is foil backed, this acts as a vapour control layer, just that any holes around light fittings need to be sealed up properly.

(1) a breathable membrane is what is used under slates/ tiles instead of old fashioned felt
(2) correct
(3) the attic floor joists are inside your heated zone as you will heat the attic room so no condensation will occur in the insulation placed between the ceiling and the floor of attic room
(4)google vario membranes

cerastes

For clarity, when I previously mentioned foil backed, I meant foil backed plasterboard as used in ceilings, or mine anyway.

Not sure Im convinced of the kind of foil used to layer the underside of roofs as Ive seen online (looks like a bubble wrap in foil) as a means to trap heat as it would have to be radiant heat? in other words direct from the source of heat. If the heat source was at a low level or even at normal output for irish housing, I consider this would not save anything or have a worthwhile return.
On the other hand, insulation that limits the transfer of heat by conduction.

Are there any issues with dry rot (mould) enclosing spaces in an attic/roof structure?

BryanF

cerastes wrote: »

Are there any issues with dry rot (mould) enclosing spaces in an attic/roof structure?

yes
An attic typically needs natural ventilation.

cerastes

BryanF wrote: »

yes
An attic typically needs natural ventilation.

I meant spaces completely enclosed, like the ceiling/floor of the upper floor and newly converted attic AND some of the roof structure may be encased/not exposed to natural ventilation.

My roof is a prefab truss frame, looking at the size of the apex beams, they seem rather thin, I suspect Id have to get them beefed up, at some point, some parts of the trusses would be enclosed in insulation, how do they deal with completely enclosed spaces for the purpose of dry rot, without introducing a channel cold air can travel through?

BryanF

Section 2 roof ventilation p28'ish http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf

So have I got this right, you converted the attic but didn't vent the Unheated roof spaces, and then separately your concerned the structure is not adequate?

cerastes

BryanF wrote: »

Section 2 roof ventilation p28'ish http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf

So have I got this right, you converted the attic but didn't vent the Unheated roof spaces, and then separately your concerned the structure is not adequate?

I havent converted anything yet, be a while away yet anyway, these are just musings, but this it is one of many considerations I think need to be addressed, ie dry rot. I dont know where dry rot occurs or under what conditions, I was meaning spaces that are sealed but would be subject to heating like the space between attic and ceiling below it.
Im aware the roof joists would be ventilated (but if insulation is fitted between them, even allowing for the 50mm ventilation space, does that mean its not ventilated all the way?) My roof trusses appear to need beefing up if they were cut to fit a room in the space, any supporting beams would be partially buried in insulation, problem?

I dont believe an attic space is viable or worthwhile if its just lashed up by knocking some wood, insulation and plasterboard together. I'm not saying that isnt hard work or people doing that dont know what they are doing, but I prefer to have real considerations measured and determined in advance, along with best use of the space and how the space works, without leaving pockets of dead space or uninsulated places, and has access to any buried services in the event they need to be accessed for something, ie water tanks, supply pipes to them etc. So to me its what makes best use of as much as possible of the available space without compromising on insulation paying consideration to detrimental side affects.

I see houses obviously with the space converted, windows etc, but with problems, tiles raised where birds could gain access to nest (ie future maintenance problem due to poorly fitted velux, maybe damp if water doesnt drain off it correctly.
One big one, is a house with an attic converted, I see where snow falls on the roof, it melts quicker than other houses which seem to do so at a similar rate, presumably these other houses have similar insulation, likely even the original, meaning, they altered the house for more space, but it was done without regard to consequences that will cost more to rectify.

BryanF

Typically the risk of condensation leading to mould/rot in timbers happens at the heated envelop meeting with the external/Unheated space. To avoid this you provide a continuous vapour barrier to the warm side of the insulation.

cerastes

BryanF wrote: »

Typically the risk of condensation leading to mould/rot in timbers happens at the heated envelop meeting with the external/Unheated space. To avoid this you provide a continuous vapour barrier to the warm side of the insulation.

ok, I was just never really certain where dry rot developed or why. I wondered how it might affect an attic conversion, but Id thought many conversions could be affected, didnt realise dry rot required some/any moisture.
I thought it was to do with the lack of ventilation but wondered why enclosed places in the home away from ventilation didnt develop dry rot, even in colder areas, like in houses with a raised wooden floor. Ive seen where some have ventilation bricks, others blocked others none to be seen.

BryanF

cerastes wrote: »

ok, I was just never really certain where dry rot developed or why.

don't get hung-up on the term dry rot

roof spaces need ventilation, internal warm moist air, should be kept away from these spaces

cerastes

BryanF wrote: »

don't get hung-up on the term dry rot

roof spaces need ventilation, internal warm moist air, should be kept away from these spaces

I dont want to keep plugging for answers, and although I see RH of below 87% mentioned there, so finally
I have seen where the ends of cut beams painted in a red or green treatment, presumably to inhibit moisture ingress on the cut section,
While Im sure its considered the preferred option to prevent the conditions of rot, is wood treated to limit or prevent it anyway or can it be? ie something like creosote substitute or whatever could be used intternaly in structures

BryanF

yes treated timber will help, but its about designing/constructing to avoid the conditions that lead to mould/damp etc