Greetings

[S2D2]

I'm a long time lurker and very grateful for all the information shared on this forum so thought I should eventually contibute.

 

Sadly self build is not on the table in my area and housing stock variety is also limited. We have an average sized four bed detached house built in the mid 1990s which means we have some insulation on one hand and suffer from plasterboard tenting on the other hand. Newer more insulated housing is available but the compromise on garden space/being overlooked is too high for us. I'll save specific issues/projects for other threads but am mainly interested in improvements for buildings of this era where insulation was barely a consideration and airtightness was ignored.

 

Thanks again to all those sharing their knowledge, it was a great help to previous projects like replacing the kitchen including subfloor.

[Marvin]

Greetings @S2D2

 

I have to ask... what was meant by the phrase "plasterboard tenting" 

 

As for air-tightness of an older building, well little things can add up to alot of improvement. Here are my cost effective suggestions:

 

With airtightness I always look at every hole in the outside of the building. Many times services passing through the external walls are not sealed properly. A bit of external sealant will do the trick.

 

Old pipe holes through the external wall not mortared need to be filled.

 

Check around windows outside and under all external window cills for gaps. Again frame sealant will do the trick.

 

Cavity walled buildings have air passing between the 2 layers of external wall so if a pipe is not sealed on the inside the air from the cavity will enter the building.

Check all possible pipes internally for gaps and seal where required.

 

Bathrooms can be a nightmare - from holes in walls where pipes pass through to no floorboards under the bath.  Pipes boxed often have hidden holes or bits of floor missing.

 

Check for poor sealing external openings. Sometimes draft excluder will do the trick.

 

Internal soil stacks often have the round pipes going through square holes. If you can get to them, seal them up.

 

Internal joists are supported by the internal layer of the cavity wall. When installed they should be sealed around otherwise the air from the cavity will get in. Any time your doing work which exposes these joists Check to see if they are sealed. If not, a big hole a bit of mortar or a small hole a bit of mastic will do the trick.

 

On suspended floors air can flow between through the join between walls and floors. ( This sometimes makes the edges of carpets next to the skirting dirtier than the rest of the carpet. On light carpets often a grey edge to the carpet).

If you get the chance seal between the floorboards and the bottom of the skirting with mastic.

 

If you have other floor finishes you can seal between the top of the finish and the skirting but use a suitable sealant as it will show. ( A white Dow corning 785 for water areas with vinyl perhaps, and a suitably coloured sealant for wood floors.

 

In cupboards with tanks or pipes in check the floors and ceilings for holes and fill where required. 

 

Check the front door letterbox shuts properly and either mend or replace. The same goes for cat flaps.

 

Check that your loft hatch seals correctly. Use draft excluder where required. 

 

External overflow pipes to old toilets allow air to blow back up the pipe and into the room. Next loo installed needs to have an internal overflow.

 

When all this is done, you may find humidity becomes a problem. The moisture was originally blown out of your home with all your heat. If so invest in fans for wet areas. Fans are usually best when they have humidity controls and mechanical shutters built in. This will mean they only come on when damp and stop drafts when not in use.

 

Boilers that are not room sealed require a supply of outside air to run and so somewhere there should be an air brick. Next replacement make a room sealed one.

 

Open fires or, log burners that are not room sealed, also require air as above. Using open fireplaces can be comforting but when not in use the air is soon replaced.

 

NOTE: Take into consideration that if you manage to seal your home up tight you need to have a way of refreshing the air that your breathing!  The 3 main ways to do this is leave a window/door open, have trickle vents or mechanical ventilation installed. 

 

Good luck with staying cosy.

 

Marvin.

 

[S2D2]

Hi @Marvin, thanks for the great response! By plasterboard tenting I mean we have dot and dab plasterboard, not edge sealed and internal penetrations also not sealed, so we have an air current behind the plasterboard from the cavity and loft. There are probably other names for it as I believe it's a common issue in modern-ish houses where care was not taken during construction.

 

Your post is basically a list of the issues with our house when we moved in and is a great reference for anyone in a similar position. Here's a summary of what I've done around these issues so far:

• External penetrations sealed around pipes etc.
• One window frame sealant redone, I need to get round to the rest as they all have gaps
• Several internal penetrations sealed when possible, tv aerial holes, water main penetration etc. Bathrooms are indeed a pain as I can't get to the pipes due to built in cupboards that were installed before we moved in
• Intumescent brush seals on integrated garage door to house
• Flexible expanding foam and sealant applied to all of upstairs junction between chipboard floor and skirting before new carpet was laid
• Slip layer on floating chipboard floor lapped up behind skirting board when kitchen subfloor was replaced and taped to plasterboard
• Letterbox replaced for a better sealed version with draft brushes
• Loft hatch replaced with Manthorpe GL250, old one had no seal whatsoever
• Chimney sheep and cap fitted to disused chimney
• Humid/stale air upstairs was indeed a problem, I installed a Nuaire Drimaster PIV system which solved it overnight, the air is much fresher. This is coupled with a trickle extractor in the main bathroom with humidity/switched boost.
• Felt lap vents fitted in the loft to prevent an annual two-week January phenomenon where condensation would go crazy and effectively rain in the loft
• Loft lids fitted to downlights in the loft, sealed to plasterboard to allow insulating over

Separate thread on loft insulation to come, watch this space!

[tonyshouse]

There is a section on the DraughtBusters website that might be of interest and helpful https://readinguk.org/draughtbusters/going-further/dot-and-dab/

[Radian]

7 hours ago, S2D2 said:

Felt lap vents fitted in the loft to prevent an annual two-week January phenomenon where condensation would go crazy and effectively rain in the loft

Not sure what you mean by Felt lap vents? Curious to know though!

[S2D2]

42 minutes ago, Radian said:

Not sure what you mean by Felt lap vents? Curious to know though!

Manthorpe G630 is what I used every other truss at the lowest overlaps. I have the bitumen type felt so the only ventilation was from the eaves and there were nowhere near enough soffit vents fitted to prevent condensation at the coldest point of the year. These vents just open up the overlap between the felt a little bit and seem to have done the trick, I pulled the felt open by hand before buying and a fair amount of airflow does come through.

 

Thanks for the link @tonyshouse, I came across this when I was doing the subfloor and paid a lot of attention to foaming up appropriately when I had access to the beam and block floor. There's a great design feature in my house where the pipes run under the floating floor (chipboard on 50mm polystyrene) with big gaps either side of the pipework. Coupled with a few leaks in the beam and block floor this means airflow can traverse the entire downstairs central heating circuit. Whilst I had the kitchen floor up I switched out for PIR taped at seams and fitted pipe insulation, but this has only improved approx 25% of the floor area. The gaps the builders left in the polystyrene were absolutely ridiculous.

[Radian]

10 hours ago, S2D2 said:

Manthorpe G630 is what I used every other truss at the lowest overlaps. I have the bitumen type felt so the only ventilation was from the eaves and there were nowhere near enough soffit vents fitted to prevent condensation at the coldest point of the year. These vents just open up the overlap between the felt a little bit and seem to have done the trick, I pulled the felt open by hand before buying and a fair amount of airflow does come through.

 

OK, thanks, not seen those before. Like you, I've also got bituminous felt but the house was built with eaves vents between every truss. 0.5m² when I totalled it all up, so no shortage of ventilation. If you live in a rural area one issue you might run in to is cluster flies which live in fields during the summer and your attic in the winter. ?