# Improving airtightness



## ATC110 (2 Jan 2012)

Hello all,

Having had problems with heatloss since moving in to a new house six years ago, I recently used a blower door to identify air ingress, it showed up the following areas:

1) Ground floor skirting boards - where the finished floor has shrunk slightly & left a narrow gap
2)Around the window boards and window frames - where the frame meets the wall
3)First floor skirting boards - possibly poor pointing where the joists enter the wall and the fact that the concrete blocks in the first floor cavity are air permeable
4)There is also a significant problem with heat retention in a room above an integral garage. It has three external walls , an internal cavity party wall between it and the rest of the house, a 225mm thick floor with 200mm of insulation in it & a dormer roof
5) There appears to be heatloss through the corner pieces of a 2.4m x 1.2m bay window

The course of action recommended is as follows:

1)Seal gap between finished floor and wall around perimeter of house
2)As above with window boards & frames
3)Cut a track in the ground floor ceiling around the perimeter of the building and insulate the block wall between each joist and around the joists
4) Internally insulate the party wall - on both sides - as this is only partially filled with cavity insulation. 
Internally insulate the ceiling. 
Cut track in perimeter of garage ceiling below, fill the 25mm gap in the ceiling / floor cavity by bunching up insulation, hold it in place with pieces of rigid insulation board, then fill the remainder.
Also seal the block wall/joists as mentioned above.
5) Coat corner pieces in Aerogel or similar and cover with uPVC moulding.


I would appreciate any comments on the above-mentioned course of action.
This would be to improve the air tightness and hopefully negate the need for external or internal insulation and/or new windows. 

I also have the following questions:

What type of sealant should be used for the finished floor gap & window boards/frames? Would ordinary caulk/ mastic be suitable?

What would be the best way to insulate between/around the joists? It was suggested to use spray foam and/or rigid insulation sheets cut to size but I'm concerned about off-gassing of these products and the likes of aerogel.

I came across this product online [broken link removed] - Would it be suitable?
Also, is there a non-toxic spray foam available?


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## Sandals (3 Jan 2012)

although I cant help you, I would assume from reading you found the test worth it, how much did it cost? Thanks.


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## Billo (3 Jan 2012)

ATC110,

Can you edit your post to remove duplication ? 

... or a I seeing double


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## Leo (3 Jan 2012)

ATC110 said:


> What type of sealant should be used for the finished floor gap & window boards/frames? Would ordinary caulk/ mastic be suitable?


 
Use standard decorators caulk, this is over-paintable when dry. 

I've removed the duplication from your post.
Leo


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## lowCO2design (3 Jan 2012)

ATC110 said:


> Hello all,
> 
> Having had problems with heatloss since moving in to a new house six years ago, I recently used a blower door to identify air ingress, it showed up the following areas:
> 
> ...


I'm afraid there are so many assumptions to be made here i don't know where to start. the wood fibre board looks good, look for the BBA cert to see how it should be used/installed correctly - also consider how you will seal it at junctions. i would recommend you use products from siga or proclima as they have guarantees, over the use of caulks where appropriate. its good to see your concerned about off-gasing etc but you havent mentioned your homes ventilation strategy? 


ok
ok. will the surface window/frame temp be cold and have condensation forming on it and will this water be able to drain away after silicone is applied?
ok but is this about air-tightness or insulation?
how do you insulate both sides of a party wall? do you mean garage wall? will you be pumping the cavity? bunching up insulation? fill with what?
aerogel is a great product i use it in new dwellings for difficult details but again are you insulating or trying to achieve air-tightness? if its the former then why are you not considering EWI? if its the latter aerogel is not an air-tightness membrane
you haven't told us what your wall, roof, floor build-ups are? what your KWH/msq/yr on heating is? or what the air-tightness test result was? dont discount more insulation, remember that our current building regs require a 60% lower energy rating than the 2005 reg home you have.. thats why the grants are available..


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## ATC110 (4 Jan 2012)

lowCO2design said:


> I'm afraid there are so many assumptions to be made here i don't know where to start. the wood fibre board looks good, look for the BBA cert to see how it should be used/installed correctly - also consider how you will seal it at junctions. i would recommend you use products from siga or proclima as they have guarantees, over the use of caulks where appropriate. its good to see your concerned about off-gasing etc but you havent mentioned your homes ventilation strategy?
> 
> 
> ok
> ...



Thanks for your detailed reply. 

The ventilation is provided by trickle flow vents on the windows - is that what you're referring to?

In answer to numbered points:

2) I've never noticed a condensation problem on the window frames/glazing.

3)Moreover air-tightness, the block wall in the ceiling/floor cavity is air-permeable and there may also be gaps around the joists. The insulation pieces and/or foam are a proposed method of making this area airtight. 

4) It's a cavity wall between the room over the integral garage and the rest of the house. Even if there is insulation in this wall, it will only be against one of the inner faces and therefore heat is being lost through it. 
( Regarding insulation, there was only 60mm insulation in the cavity which did not comply with building regs. so the developer pumped the cavities with insulation, in theory filling them. The garage/house party wall was done up to the ceiling but not the first floor)
By bunching up the insulation I mean pushing the existing rockwool in order to compress it to fill the ceiling cavity completely with no gaps, then use insulation board to hold it in place and then filling the remaining opened-up area with rockwool.

5) This would be to insulate the corners of the window. What is EWI? Are there potential off-gassing issues with aerogel? 


The walls are brick outer leaf, 100mm cavity with 60mm aeroboard topped up with Certainfil 27+ blown bead, block inner leaf

The loft has 350mm of fibreglass in three layers laid at right-angles on two sides of the loft.
The middle section has 250mm of insulation with counter battens in oder not to compress it and then chipboard sheets for flooring

The ground floor has rigid insulation in the concrete floor. No insulation in first floor

I can't give you an accurate figure on the heat input as the heating is not regularly used do to it's ineffectiveness.

The previous air-tightness test carried out five years ago was 4.31 when the UK minimum standard was 10 so it was well within the limits.

Regarding extra insulation, the only remaining options are internal or external insulation and/or triple-glazed windows, either of which would be expensive.

Thanks again.


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## serotoninsid (4 Jan 2012)

ATC110 said:


> What is EWI?


External Wall insulation


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## lowCO2design (8 Jan 2012)

hi ATCII0, as per your email request for a reply to your post

insulation: I refer to your final statement above and suggest that  (without a site visit) my assessment/ suggestion is that EWI is your  best and most comprehensive option. but dont get a half assed EWI job  done, its important that its is detailed correctly preferably by an  arch/arch tech with pasive house expericen that they will at least be  cognisant of the details required to achieve air-tightness and thermal  bridge free details. have you seen the recent Duncan Stewart show where a  house like yours was retro-fitted to passive standards: basically MVHR,  EWI and Triple glazed windows

now your air-tightness is more interesting and I beg people to consider  this when trying to achieve greater air-tightness levels in their homes.  on the one hand you say you have an air change rate of 4.31 (AC/per hr @  50p i persume?) on the other you have only trickle vents in your  windows.. if you go much lower with your air-tightness measure, your  getting to levels where whole house mechanical ventilation begins to be  necessary (note MV will not necessarily be efficient until much lower  levels of air-tightness are achieved). one factor not considered by me  here is what size the house is or the number of occupants, as you could  argue the volume of the house allows for greater levels or air-tightness  before MV is required, especially given that no signs of condensation  are evident 

3. foam & insulation will only do so much, an air-tightness membrane  and tape/caulk   would better but near impossible to install in tight  spaces 
4. pump the cavity. if you compress mineral wool insulation it does not  necessarily give it any more thermal resistance. the general solution  for the walls will help your heat loss issues
5. ive used aergel this is this situation, not really sure about off-gasing, its a silicate material so I don't see how. re EWI the amount of insulation you have and the nature of windows manufactured and installed in recent years, suggests to me that EWI and new CAREFULLY SELECTED windows would improve your situation best. 



> I can't give you an accurate figure on the heat input as the  heating is not regularly used do to it's ineffectiveness.


??? what size is the house? and what is way is it heated?


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## ATC110 (8 Jan 2012)

Thanks again for your reply.



> insulation: I refer to your final statement above and suggest that  (without a site visit) my assessment/ suggestion is that EWI is your  best and most comprehensive option. but dont get a half assed EWI job  done, its important that its is detailed correctly preferably by an  arch/arch tech with pasive house expericen that they will at least be  cognisant of the details required to achieve air-tightness and thermal  bridge free details. have you seen the recent Duncan Stewart show where a  house like yours was retro-fitted to passive standards: basically MVHR,  EWI and Triple glazed windows



Yes, I appreciate that but it would be expensive-it's a detached house with integral garage approx. 2150 sq.ft.

Could you suggest an architectural technician/architect conversant with air-tightness and and thermal bridging?

Do you know when that programme was broadcast?



> now your air-tightness is more interesting and I beg people to consider  this when trying to achieve greater air-tightness levels in their homes.  on the one hand you say you have an air change rate of 4.31 (AC/per hr @  50p i persume?) on the other you have only trickle vents in your  windows.. if you go much lower with your air-tightness measure, your  getting to levels where whole house mechanical ventilation begins to be  necessary (note MV will not necessarily be efficient until much lower  levels of air-tightness are achieved). one factor not considered by me  here is what size the house is or the number of occupants, as you could  argue the volume of the house allows for greater levels or air-tightness  before MV is required, especially given that no signs of condensation  are evident



House is 2150 sq.ft with two to three occupants.



> pump the cavity. if you compress mineral wool insulation it does not  necessarily give it any more thermal resistance.



The cavity wall has been pumped - in the garage below but not the room above hence the suggestion to dry-line.

What do you suggest to do to the garage ceiling cavity if not to bunch up the insulation?



> re EWI the amount of insulation you have and the nature of windows manufactured and installed in recent years, suggests to me that EWI and new CAREFULLY SELECTED windows would improve your situation best.



Again, could you recommend / suggest companies for the EWI and triple-glazed windows? YOu can send me a PM if you prefer.



> ??? what size is the house? and what is way is it heated?



As above and oil-fired central heating via radiators.


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## lowCO2design (8 Jan 2012)

where in the country are you? I should have stated from the  beginning I'm an arch tech, but I was not offering you this advice in  the hope of work, it just my opinion as i deal with these issues  regularly
sorry, I don't know which program it was shown but there have been  several interesting retro-fit jobs shown recently, my point was that  their home was badly built of a similar age to yours
cavity pump the wall above
its the term 'bunch up' that im not sure about, using mineral wool or similar breathable material is fine
I would simply say go to a european EWI system manufacture that has  a long history and ask for a list their local installers. windows like  with the EWI contractors i have my preferences, but must have control  the materials, performance spec/ detail drawings and hold a % of the  price back until the products are installed and checked insitu often  with thermal imaging &/or air-tightness test
there is no reason why your heating system should not have been  designed for your home fabric performance. the air-tightness and  insulation should merely reduce the cost/amount of time your heating  operates. get a plumber out to check its operating correctly


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## ATC110 (9 Jan 2012)

.....


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## ATC110 (9 Jan 2012)

lowCO2design;1232746

1) where in the country are you? I should have stated from the  beginning I'm an arch tech said:
			
		

> 1) North East - I note you're in Cork so it's not feasible for you to travel. Do you know of anyone in this area?
> 
> 3) I'm reluctant to do this for the following reasons:
> 
> ...


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## lowCO2design (9 Jan 2012)

3. i dont share your concerns, once the installer is competent & product suitable
5. no, unfortunately its best to let a third party do this test - although you said you had an air-tightness test done already, so surely he offered you a reduced rate to return following the work?


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