Aerobarrier booked for Tuesday

[Post and beam]

If you are having a cold roof then the airtight boundary at the upper floor ceiling will not be provided by them for example. This is a shed load of work.  All well and good if you are expecting this but a big suprise if you are not. They dont board the loft or fit the 400mm rockwool either. They just deliver a lorry load of it. Again, fine if you know this. Not so much if you dont.

[LnP]

7 minutes ago, Post and beam said:

They do 3 basic types of house the old dormer cottage style like the gransden show house. The georgian style and the much more modern looking things. Even a passive version.  I suggest reading their terms very carefully, they have many years experience and de risk everything they say. Whatever target airtightness you end up with remember that they write ' final airtighness is down to'  .... others. If you are not taking the full turnkey package then there is so much left to do that will not be done by them that the target is meaningless. It will not be their fault when the target is not reached. I have learnt a great deal while building mine about Potton details and standards.Are you a competent DIYer or a builder yourself? There are things i might be able to help with regarding them. Where are you in the country? Keith

 

Hmmm. Food for thought. I plan to self manage and have as little hands on the tools myself as possible. I'm fairly well plugged into a network of good local trades who've worked for me before (not a full self build though) and have told me they will be happy if they're invited back. I have a friend who's a builder and is happy to advise and get me out of trouble.

 

Tricky when you don't know what you don't know though. I've had quotes from four timber frame companies and asked them all the same open question, what will be left for me to do when you leave the site? And I've tried to estimate the value of the different scopes to compare the quotes on a similar basis. I suppose this is what the contingency is for?

 

I'm in Cheshire. I'd appreciate any advice you can share. I'll drop you a DM.

[Nickfromwales]

9 hours ago, Post and beam said:

This is why i announced before hand that they were booked. I imagined at least one or two selfbuilders would have been interested

1) I'm not lucky enough to be self-building yet......

2) I often don't see the woods for the trees.....

[Nickfromwales]

7 hours ago, Post and beam said:

5 is not much of a score for them to aim for as a 'premium' supplier, i think all the major house builders would give you that figure

It's a bit like leaving a fecking window open...... utter shite.

 

All these sorts run for the hills when you ask them to turn up the dial on GAF. Shocking tbh.

 

57 minutes ago, Post and beam said:

They do 3 basic types of house the old dormer cottage style like the gransden show house. The Georgian style and the much more modern looking things. Even a passive version.  I suggest reading their terms very carefully, they have many years experience and de risk everything they say. Whatever target airtightness you end up with remember that they write ' final airtightness is down to'  .... others. If you are not taking the full turnkey package then there is so much left to do that will not be done by them that the target is meaningless. It will not be their fault when the target is not reached. I have learnt a great deal while building mine about Potton details and standards. Are you a competent DIYer or a builder yourself? There are things i might be able to help with regarding them. Where are you in the country? Keith

 

Amen!

 

Soooo many people invest their trust in so-called turnkey providers......like a moth to the flame afaic.

[Kelvin]

21 hours ago, Post and beam said:

Results are in. 

 

3.9 as built air permeability prior to Aerobarrier doing their thing.

 

Ended up with a figure of 1.4, so a 63% reduction.  

 

The structure surface area was calculated as 479 square metres.  I dont know how this would relate to an ACH  figure. 

From 1.62 to 0.58 so a great result. 

[Post and beam]

1 hour ago, Kelvin said:

From 1.62 to 0.58 so a great result

Hi Kelvin. Is that the ACH  then? 

[JohnMo]

22 minutes ago, Post and beam said:

Hi Kelvin. Is that the ACH  then? 

Without knowing your house volume he cannot know that!

[Kelvin]

Sorry no ignore me. I misread your earlier message and thought you’d posted your internal air volume. You need to work that out. Then it’s 1.4 x 200 divided by the volume. 

[Kelvin]

Just now, JohnMo said:

Without knowing your house volume he cannot know that!

Yes sorry I misread his post. 

[JohnMo]

12 minutes ago, Kelvin said:

1.4 x 200 divided by the volume

Are you sure, I think it's (1.4 x 479) / volume.

 

So if house is 200m² and ceiling are 2.4m high is 200 X 2.4 = 4800.

 

(1.4 x 479) / (2.4 x 200) = 1.4 ACH

Edited Wednesday at 08:09 by JohnMo

[Post and beam]

3 minutes ago, JohnMo said:

So if house is 200m² and ceiling are 2.4m high is 200 X 2.4 = 4800.

 The house is a dormer upper floor with some sloping ceilings. These will eat into the calculation, but are then offset by the fact that we have a slightly vaulted ceiling in the dining room. 

So on balance i think we have slightly less than 4800, but only by about 10 cubic metres. 4800 is a nice round number.

 

Going on a calculation i saw on the intergoogle the surface area divided by the volume gives the SV ratio.

479/ 4790 = .1

Does that look correct? have i got that right?

 

[JohnMo]

Your answer is pretty much 1.4 ACH

[Post and beam]

I had the volume wrong so my calculation would have been nonsense.

Area = 479

Vol = 479

Big coincidence

 

Off by a factor of 10

 

So ACH = 1.4 X 1 = 1.4 

 

Thanks @JohnMo, agrees with your number. confirmation bias? but i am happy with that

[JohnMo]

We have a long thin house, so way different from factor yourself, it didn't change our test result much when converted to ACH.