Improving airtightness

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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 http://www.greensteps.co.uk/tmp/assets/1210866730018.pdf - Would it be suitable?
Also, is there a non-toxic spray foam available?
 
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I would be concerned with sealing a building as you are doing. A building has to breath, if it is sealed as you are doing you will have problems with condensation and rotting of timbers.
 
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the off gassing happens after manufacture (or in the case of spray foam, when it is setting). So rigid foam, having sat around warehouses for x time before you buy it will not be an issue.

Don't know about spray foams, but I have not come across any issues.

As I like to point out, everyone loves that new car smell, well, that's toxic off gassing at a concentration higher than in most building products (excluding dodgy plywood), you like the new car smell right?



Air tightness and breath ability are not the same. It depends on how well insulated your building is, and if it has any bad cold bridging spots as to weather making it airtight will cause condensation. The block frame will be very breathable, and if it is insulation, condensation will not occur on the inside of the building (except at cold bridges), and if you have vapour layers on the warm side, and vapour that does get through, will "breath" out past the block/insulation.

If you make it airtight/vapour impermeable, but have cold bridges, then this is where condensation will occur.

The problem is a lot of stock brick n block buildings are very poorly made, and so it's difficult to maintain the right balance without proper modifications.
 

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