Cost of airtightness retrofit?

[anonymous]

I've got a 1975 timber frame semi detached 120 square ft house, which is already well insulated but I want to make sure it's air tight. There's no point having insulation if I'm leaking air and it's costing me £7/day just to maintain one temperature.. 

 

I understand that obviously the cost of getting it to be air tight can be quite different, but I was wondering how much such a thing has cost others? 

 

I'm getting an air tightness test next week 

 

Thanks 

[Olf]

  On 08/12/2022 at 19:52, anonymous said:

getting it to be air tight can be quite different

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There is your answer: if the airtight tests (very good idea, will allow to make informed decisions! ) finds only specific holes/gaps/cracks, you may end up with spending 2 hours with £10 can of Illbruck.

Or if the whole structure is one big sieve, multiple of £60 cans of blowerproof and goth decor 🤪

 

[anonymous]

  On 08/12/2022 at 21:19, Olf said:

There is your answer: if the airtight tests (very good idea, will allow to make informed decisions! ) finds only specific holes/gaps/cracks, you may end up with spending 2 hours with £10 can of Illbruck.

Or if the whole structure is one big sieve, multiple of £60 cans of blowerproof and goth decor 🤪

 

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So probably under 1K to get it air tight? 

[Roundtuit]

Impossible to say really.  It depends on where the leaks are.  Unless you're stripping it back to basics, all you can realistically do is plug the holes in the inner skin (caulking round skirting etc); the cold air may still be circulating behind the plasterboard and negating the insulation.  I'm guessing you have trickle vents in the windows?  Perhaps not much benefit in sealing up too much unless you can control ventilation losses.

[Olf]

  On 08/12/2022 at 21:49, anonymous said:

So probably under 1K to get it air tight?

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Might as well be, but the question is if this is money well spent: completely sealed building will still loose energy if the walls conduct. Passivehouse will loose energy if you open all the windows.

The most economical option is when conductive (through floor, walls, ceiling) and convective (draughts) losses are similar - so if you have budget of 1k, it may be that you attack the biggest holes, but spend the rest on loft or other areas. Not to mention that even if your own labour rate is nil, getting extra detail sorted out takes exponentially longer.

Also some of the jobs have cost of disruption or require redecoration afterwards. And to finish, if you're too well sealed and do not have precautions (ventilation, preferably with heat recovery, but that is another cost), moisture and CO2 levels will climb up, and that can cause new problems...

[jfb]

Also be aware that if you get below a certain level (3 ach/hour I think) you should have mechanical ventilation. That isn’t an easy retrofit and probably not something to worry about depending on the test score and work you undertake.

[saveasteading]

  On 08/12/2022 at 19:52, anonymous said:

I'm getting an air tightness test next week 

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Do they know that you are looking for weaknesses? ie that they aren't just testing , but going round with a smoke stick looking for gaps?

If they were to do the test, then pack up and leave without you knowing where the problems were, it wouldn't be much help.

 

Remember to close trickle vents and blank off all extract fans in advance.

 

Edited December 9, 2022 by saveasteading

[Iceverge]

BUILD edqdwdwded your own rig. 

 

Ingredients.

 

1. A sheet of OSB.

2. A scrap car radiator fan. 

3. Some screws. 

4. Some duct tape or similar. 

5. A length of wire and crocodile clips.

6. A length of electrical conduit

7. A candle that will slot into the conduit.

 

Total cost < £100. 

 

Method.

 

1. Measure an opening ( outward preferably) window sash and cut the OSB to the same size so it slots in against the seal in place of the sash. 

 

2. Cut a suitable hole and screw the car radiator fan into place in the OSB. 

 

3. Tape the OSB and fan to ensure no leaks in the window. 

 

4. Use the wire + crocodile clips to connect the fan to your car battery. (Leave the car running to avoid a flat battery) 

 

5. Ensure the fan is pulling air out of the house. ( You can reverse the fan or swap polarity on the battery if you get it wrong)

 

6. Go room by room with the back of your hand (big leaks) and the candle in the conduit ( small leaks) and seal each and every tiny hole with proper expanding foam or age proof flexible sealant. 

 

[anonymous]

  On 09/12/2022 at 10:27, saveasteading said:

Do they know that you are looking for weaknesses? ie that they aren't just testing , but going round with a smoke stick looking for gaps?

If they were to do the test, then pack up and leave without you knowing where the problems were, it wouldn't be much help.

 

Remember to close trickle vents and blank off all extract fans in advance.

 

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They know that I'm going for PassivHaus compliance but not necessarily the certification 

 

They also know they they'll tell me how to remediate them 

[anonymous]

  On 09/12/2022 at 10:19, jfb said:

Also be aware that if you get below a certain level (3 ach/hour I think) you should have mechanical ventilation. That isn’t an easy retrofit and probably not something to worry about depending on the test score and work you undertake.

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Yup. I've already got a ballpark quote from the "greenbuildingstore" RE: an MVHR 

[Sparrowhawk]

@anonymousHow did you get on with your airtightness test, and what did they find?

[anonymous]

  On 01/01/2023 at 22:18, Sparrowhawk said:

@anonymousHow did you get on with your airtightness test, and what did they find?

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Hey

 

Sorry. I haven't been here for a while. I got a score of 7.66 and mostly they found draughts around windows / doors + they odd bit of piping

 

So I've got some of that sealed up. Though realistically, given I noticed condensation on the odd window, I'll probably get shut of them anyway as part of my long term plan 

[Iceverge]

Get some simple ventilation going. 

 

So long as you have some air somewhere being mechanically pushed into or drawn out of the building 24/7 it'll make a noticeable difference to humidity levels. 

 

Low humidity means everything feels warmer. 

 

In our old rental cottage I used to leave the kitchen extractor on and the internal doors open while we were out for the day. It ensured that any damp stale air was well diluted and removed from the house. It made a noticeable difference. 

[Sparrowhawk]

  On 09/12/2022 at 10:46, Iceverge said:

Ingredients.

 

1. A sheet of OSB.

2. A scrap car radiator fan.

 

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As scrap car radiators fans on ebay seem to go at a premium at present, would one of these 12" fans or these 16" fans be powerful enough to do the job? They're listed with the same CFM so I'm thinking the smaller one.

[Iceverge]

Should be. The bigger the better I say. Maximum attack!!

 

One point I would note is that the flange area around the edge seems minimal. You would be left trying to cut a very accurate hole and tape to the bare minimum the remainder. 

 

Something like this would be twice as powerful and easier to fit. Just get the seller to include the plug and a few cm of wire when posting it. 

 

[MikeGrahamT21]

And don't forget to turn off your gas appliances, including boiler!

[Sparrowhawk]

  On 19/01/2023 at 08:43, MikeGrahamT21 said:

And don't forget to turn off your gas appliances, including boiler!

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Why's that? Aren't boilers sealed units venting to the outside only?

[Nickfromwales]

  On 19/01/2023 at 09:57, Sparrowhawk said:

Why's that? Aren't boilers sealed units venting to the outside only?

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If it’s an RS ( room sealed ) appliance, yes.

Look to see if it’s a coaxial flue ( pipe in pipe ).

[Nickfromwales]

  On 09/12/2022 at 11:05, anonymous said:

They know that I'm going for PassivHaus compliance but not necessarily the certification 

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That means a attaining a very ( very ) good AT score? That would be sub 0.6ACH with 1.0 being quite admirable. 

[MikeGrahamT21]

  On 19/01/2023 at 09:57, Sparrowhawk said:

Why's that? Aren't boilers sealed units venting to the outside only?

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They are, but its better to be safe than sorry. Boilers (and any gas appliance) shouldn't be operational in negative pressure atmospheres