cavity wall insulation

Andy From Sligo

hi - just wondering can cavity wall insulation be applied from inside the house into the cavity?

and question number 2 (its a dormer house we have) and its this - why would it have cavity wall insulation on the downstairs part of the house but seems there is no cavity wall insulation upstairs?

Question number 3 what is more effective cavity wall insulation or adding more loft insulation? the upstairs rooms feel like a fridge when the heating goes off whereas the downstairs keeps warmer for longer - I have been up in the loft and the landing area has been topped up with nice deep (got to be at least 6") fresh fibreglass on top of the previous compacted fibreglass but over the bedroom and bathroom it looks all compacted and about 4" if that - what would save more heat out of the 2? more loft insulation or apply Cavity wall insulation ?

thanks all..

Metric Tensor

1. Yes you can pump a cavity wall from inside but it's a messier proposition because you have to redecorate inside and it is more difficult for the installer because he has to drag equipment from room to room inside your house.

2. If it is a dormer house there should not be cavity walls upstairs apart from the gables at either end. You dormer windows (if that's what you have) would be built in timber stud just like the rest of the roof structure.

3. Attic insulation is better value for money, it costs less and saves more - so you should go with that first. However, if you have a dormer, as you've described, you should have two different (difficult to reach) attics and only the upper one of these two would relate to the temperature upstairs. You should also most likely have attic side walls and "hidden" sloped insulation to think about.

Any chance of a picture of the house because what you describe doesn't sound like a "traditional" dormer as I would picture it.

Andy From Sligo

Metric Tensor wrote: »

1. Yes you can pump a cavity wall from inside but it's a messier proposition because you have to redecorate inside and it is more difficult for the installer because he has to drag equipment from room to room inside your house.

2. If it is a dormer house there should not be cavity walls upstairs apart from the gables at either end. You dormer windows (if that's what you have) would be built in timber stud just like the rest of the roof structure.

3. Attic insulation is better value for money, it costs less and saves more - so you should go with that first. However, if you have a dormer, as you've described, you should have two different (difficult to reach) attics and only the upper one of these two would relate to the temperature upstairs. You should also most likely have attic side walls and "hidden" sloped insulation to think about.

Any chance of a picture of the house because what you describe doesn't sound like a "traditional" dormer as I would picture it.

thanks yes , I will take a pic today.

Half of the bedrooms, and the toilet and en-suit are not insulated with thick enough fiberglass, and yes would be very awkward to get to, i dont even know how that would be possible because there is a massive iron lintel in the attic that runs the whole length of the house on both sides so you cannot get to that part to insulate it with more fibreglass. - to be honest i cannot even make out how they managed to get to that area when they first built the house! - only way I can think they done it was insulate the attic *before* putting the roof slates on the house but they hardly would have done that would they?

the rooms downstairs that are cavity wall insulated (even the outer walls) are war/neutral temperature to the touch the upstairs outer walls (well hold on they are not walls as such , you can knock them like they are partitions , even the outer walls inside if you know what I mean) are cold to the touch and the bathroom is tiled (what seems to be on partition type plasterboard) and they are very cold to the touch and condensate like mad when the hot shower steam touches the cold tiles - is it possible these walls have no insulation in them at all (even aeroboard) and just have an air gap in the cavity and thats that?

The 'Slopes' in the bedrooms are cold to the touch than the other internal (partition walls) upstairs.

Here is a diagram of what the attic is like:

Metric Tensor

The upstairs "outer walls" as you call them are probably a timber stud wall that separates the upstairs from the "pink" area which I would call the side attic. I am following you correctly?

If so you need to get into this side attic and add extra insulation to the attic floor (which is the ceiling of the downstairs rooms) and to the stud wall that separates upstairs from the side attics. None of this is suitable for "pumping" in a traditional sense.

It's a nightmare of a job - but the correct one.

Andy From Sligo

Metric Tensor wrote: »

The upstairs "outer walls" as you call them are probably a timber stud wall that separates the upstairs from the "pink" area which I would call the side attic. I am following you correctly?

If so you need to get into this side attic and add extra insulation to the attic floor (which is the ceiling of the downstairs rooms) and to the stud wall that separates upstairs from the side attics. None of this is suitable for "pumping" in a traditional sense.

It's a nightmare of a job - but the correct one.

Thanks, no the area with the pink fibreglass is definately the ceiling of the upstairs rooms and not the ceiling of the downstairs rooms.

So,(without me demolishing the plasterboard) what do you reckon is in the 'slopes' of the upstairs dormer part behind them slopes - should it be polystyrene aeroboard or do you reckon fiberglass ... or even maybe nothing?

Is it worth getting someone into those rooms with an infra-red camera and just see where the heat is escaping/not insulated rather than removing plasterboard?

BryanF

Andy if you want to sort this, best thing to do is take of the tile/slate roof and felt, lay a vapour barrier, insulation and re-felt (breathable) batten counter batten and re til/slate.

Andy From Sligo

BryanF wrote: »

Andy if you want to sort this, best thing to do is take of the tile/slate roof and felt, lay a vapour barrier, insulation and re-felt (breathable) batten counter batten and re til/slate.

thanks, that does indeed sound like an extensive job that - but then again I suppose there is no easy fixes.

on another note you know that vermaculite stuff , can that stuff be blown some how (with an opposite of a vacuum cleaner) into the roof space where the pink fiberglass is? - there is no way enough gap for a person to get into that area, its just too tight , but some kind of hose blowing the vermaculite could be pointed into the area

MicktheMan

Andy From Sligo wrote: »

hi - just wondering can cavity wall insulation be applied from inside the house into the cavity?

and question number 2 (its a dormer house we have) and its this - why would it have cavity wall insulation on the downstairs part of the house but seems there is no cavity wall insulation upstairs?

Question number 3 what is more effective cavity wall insulation or adding more loft insulation? the upstairs rooms feel like a fridge when the heating goes off whereas the downstairs keeps warmer for longer - I have been up in the loft and the landing area has been topped up with nice deep (got to be at least 6") fresh fibreglass on top of the previous compacted fibreglass but over the bedroom and bathroom it looks all compacted and about 4" if that - what would save more heat out of the 2? more loft insulation or apply Cavity wall insulation ?

thanks all..

Dormer house = Massive heat loss by air leakage, not lack of insulation in our temperate but windy climate.
Have the house tested for air tightness. This, I guarantee you, will change how you think about / see the problem.

Andy From Sligo

MicktheMan wrote: »

Dormer house = Massive heat loss by air leakage, not lack of insulation in our temperate but windy climate.
Have the house tested for air tightness. This, I guarantee you, will change how you think about / see the problem.

actually i think your onto something there because even when its not that cold outside ... but its windy it can feel a lot colder upstairs.I was putting that down to not having enough insulation in the ceilings. - right, so it could be drafts then , interesting

Hurrache

MicktheMan wrote: »

Dormer house = Massive heat loss by air leakage, not lack of insulation in our temperate but windy climate.
Have the house tested for air tightness. This, I guarantee you, will change how you think about / see the problem.

I'm going to jump on one of Andy's threads, what is about dormers that make them more susceptible to heat loss due to the wind? I've a similar issue, the walls between the side attic space and adjacent rooms are insulated, as too is the main attic floor, but the roof itself isn't.

I've read before that you shouldn't insulate the roof in a dormer (or something like that), but I don't know why.

MicktheMan

Hurrache wrote: »

I'm going to jump on one of Andy's threads, what is about dormers that make them more susceptible to heat loss due to the wind?

Heat loss due to lack of airtightness, rather than lack of thermal insulation.

Hurrache

But what in their construction makes them less airtight than other builds?

Andy From Sligo

Hurrache wrote: »

But what in their construction makes them less airtight than other builds?

am intrigued too ...

MicktheMan

Hurrache wrote: »

But what in their construction makes them less airtight than other builds?

Andy From Sligo wrote: »

am intrigued too ...

Because a significant proportion of the internal conditioned space is in the roof structure and the unconditioned attic space needs to be vented so unless specific measures were taken to prevent the vented attic outside air from entering the conditioned internal space, the top of the dormer house will leak air like a sieve. A standard house is basically a cuboid and therefore does not suffer this weakness.

Metric Tensor

The joints between exposed surfaces are weak points which require careful work and detailing.

In a rectangular bungalow or two-storey there could be as few as 12. (discounting windows and doors.)

In a simple dormer house with 2 dormer windows I count approximately 50! (still discounting windows and doors.)

sydthebeat

Hurrache wrote: »

But what in their construction makes them less airtight than other builds?

a myriad of different materials used together, not specifically designed for that particular purpose.
a conglomeration of joins and junctions of these materials in a significantly small area.

Andy From Sligo

sydthebeat wrote: »

a myriad of different materials used together, not specifically designed for that particular purpose.
a conglomeration of joins and junctions of these materials in a significantly small area.

whats the solution , can not the dormer parts of upstairs be built in block and plaster like the downstairs?

Does this mean that because the way our dormer house is constructed it will always be colder upstairs than downstairs in the winter then?

Metric Tensor

They can be built in rendered blockwork but it is unusual.

In all likelihood upstairs will always be more draughty and hence colder.

BryanF has already given the best way of sorting this. Take the roof off and carry out extensive air-tightness and insulation works when you have full access from the outside. It still will not be "perfect".

You can do cheaper air-tightness works upstairs but it won't be easy nor will it be super effective - but it might be enough to make the difference you need. Some of the lads here who know more about remediation methods might be able to offer some pointers.

sydthebeat

Andy From Sligo wrote: »

whats the solution , can not the dormer parts of upstairs be built in block and plaster like the downstairs?

Does this mean that because the way our dormer house is constructed it will always be colder upstairs than downstairs in the winter then?

The solution is quite easy. Don't design them into the build for the very reasons this thread is about.
Use rooflights or wider block gables if possible.


Ultimately the role of a designer is to design out the problems.

Andy From Sligo

roofer guy came today to have a look what could be done (if anything) - but in all the questions (yes I had a few for him) he was explaining that there might not be enough of a air gap to fill out the space in the cavity and also allow for air to circulate then that would bring other problems , mainly to the inside plasterboard.

So really what i forgot to ask why the downstairs can have its air cavity filled up its air space with cavity wall insulation (look like white polysterene beads if you drill into exterior wall) but the upstairs cavity cannot be filled - I mean its quite confusing , how can you fill up the air gap in the downstairs block wall construction but the upstairs (he said was timber build) canot have cavity wall insulation because it needs an air gap .. and i would have asked also if there was cavity wall insulation that could be put into the wall that can breath and let air circulate as well as insulate at the same time - is there such an insulation?

so this is a diagram of what i think he was explaining the way our house is constructed:



So, what would happen if the air gap in the upstairs rooms where filled out with cavity wall insulation , what consequences be with no air gap? - I am presuming if the inner plasterboard has a vapour barrier/foil and aeroboard behind it how could damp get through that and if it was pumped with insulation then it wouldnt have cold air so it shouldnt get condensated or wet and the insulation being made of polystyrene beads would act as a barrier too stopping water getting from the outer (plywood) wall wouldnt it?

EDIT: just been reading this thread all the way through - it looks a resounding no no then for filling the cavity totally up in a timber frame construction
https://www.boards.ie/vbulletin/showthread.php?t=2056488433

Metric Tensor

Timber needs a flow of air to breath or it will go rotten - no way around it.

Andy From Sligo

it makes one wonder how can you accurately measure the BER rating in a house of the build such in the one we are living in , in which the downstairs is made of block and has cavity wall insulation and is warm ... but the upstairs of the house is made of timber and plasterboard and gets colder - it would put me off moving / buying another house part built with timber or a timber built house ever again, it would have to be block all the way (and cavity wall insulation) - I reckon internal plasterboard walls great for separating rooms (such as in a partition) - but useless when used on walls especially outside walls inside the house.

Metric Tensor

The BER system has many failings but to be fair to it one can include as many different wall constructions as necessary.

There are plenty of good quality timber frame buildings out there too. When it comes to buying - quality of build is more important than the specific type of construction. They all have pros and cons but a better constructed house of any type will always be better than a crap one of another type.