How to make a solid brick house airtight?

[jayc89]

A lot has been said about the negligible benefits of MVHR in a house with substandard airtightness. So what's the key to making a house airtight when renovating?

- Airtight membrane across ground floor joists? What about solid floors?
- Airtight membrane across external walls, with correct window/door detailing?

- Airtight membrane across top floor ceilings/roof?

 

There must be more to it than that though, no?

What about fireplaces? Letterboxes? Drains, or anything else, that exits through the walls rather than through a slab?

[ProDave]

14 minutes ago, jayc89 said:

A lot has been said about the negligible benefits of MVHR in a house with substandard airtightness. So what's the key to making a house airtight when renovating?

- Airtight membrane across ground floor joists? What about solid floors?
- Airtight membrane across external walls, with correct window/door detailing?

- Airtight membrane across top floor ceilings/roof?

 

There must be more to it than that though, no?

What about fireplaces? Letterboxes? Drains, or anything else, that exits through the walls rather than through a slab?

In a well insulated air tight house MVHR offers substantial advantages.  I assume the use of "negligible" was a typo?

 

Re that latter questions.  Letterbox, don't have one, a box on the wall outside.  Fireplace, don't have an open fireplace but if you want fire have a properly flued stove with combustion air ducted in directly from outside, i.e. room sealed.  Cat flap, open the door to let the cat in / out etc.  Drains won't leak air, the water traps see to that, just make sure all pipe penetrations in and out of the building are sealed.

[tonyshouse]

The stuff about negligible benefits is nonsense, try living with MVHR.

 

Wall airtightness = wet plaster. But join hermetically to the air tightness barrier in the floor and ceiling  

 

[jayc89]

1 hour ago, ProDave said:

In a well insulated air tight house MVHR offers substantial advantages.  I assume the use of "negligible" was a typo?

 

Re that latter questions.  Letterbox, don't have one, a box on the wall outside.  Fireplace, don't have an open fireplace but if you want fire have a properly flued stove with combustion air ducted in directly from outside, i.e. room sealed.  Cat flap, open the door to let the cat in / out etc.  Drains won't leak air, the water traps see to that, just make sure all pipe penetrations in and out of the building are sealed.

 

Negligible in the sense, if a house's airtightness is poor, there's no use having an MVHR. 

 

Is it really that simple though? I assume, when applying the airtight barrier internally, there will become added complication where internal walls are tied into external ones etc?

[Nickfromwales]

2 hours ago, jayc89 said:

negligible benefits of MVHR in a house with substandard airtightness

Read what the man wrote people!!!!!

 

Yes, every damn thing needs attention. Miss a couple of pipes / leaky mortar joints / etc and you are still going to lose huge percentages of the significant benefits of installing MVHR.

During an airtightness test you can even hear the air whistling through a hole made by a screw having been driven in and removed, so every minute detail need addressing......"in for a penny, in for a pound" I'm afraid.

You'll need to take the house back to its skeletal form to do this as well as it'll need doing. If you can only get halfway done, don't bother starting is the blunt, but honest answer. 

[Roger440]

When you say "solid" do you mean no cabity, just a single wall?

 

In which case, proceed with caustion as its likely to have no DPC, so your airtightness may create a host of other problems.

 

My main issue with them is noise. Some will say its not a lot of noise, minimal in some cases. But its noise all the same. 

 

Plus of course, and discussed here before, all the other buggers in the village with log burners filling up the valley with smoke. Which would then get pulled in!

[jayc89]

2 hours ago, Nickfromwales said:

Read what the man wrote people!!!!!

 

Yes, every damn thing needs attention. Miss a couple of pipes / leaky mortar joints / etc and you are still going to lose huge percentages of the significant benefits of installing MVHR.

During an airtightness test you can even hear the air whistling through a hole made by a screw having been driven in and removed, so every minute detail need addressing......"in for a penny, in for a pound" I'm afraid.

You'll need to take the house back to its skeletal form to do this as well as it'll need doing. If you can only get halfway done, don't bother starting is the blunt, but honest answer. 

I'll certainly be tackling rooms one by one (well, probably a room downstairs and the one directly above it), but I'd be aiming for a full house approach. 

 

- When using PIR, taped etc, for IWI, is an additional airtight membrane, recommended too? Warm or cold side?
- If so, should the membrane be carried around any internal wall returns, or just sealed and taped to them?

- The ground floor slab has 25mm PIR up stands around the perimeter, how should any membrane be detailed there?

- There are gaps on the cold side of the up stands, where the PIR doesn't sit exactly flush with the brickwork. Should these also be filled with foam, or something else, first (I understand foam can shrink so general avoid it)?