Having an air test next week, any tips?

[Jeremy Harris]

1 minute ago, ProDave said:

I am puzzled why he could not tell you the result immediately?  The only time I was present for one, the result was known immediately.

 

 

Same here, the results were up on the tester's laptop screen, the pressurisation, depressurisation and average plots were displayed as a graph.

[joe90]

3 minutes ago, JSHarris said:

 

 

Same here, the results were up on the tester's laptop screen, the pressurisation, depressurisation and average plots were displayed as a graph.

Ah, not sure, he didn’t have a laptop but a thing that looked like a large multimeter (Steamy may put up a piccy later) with lots of numbers on it, he also took the house plans as they are doing the as built SAP as well.

 

[SteamyTea]

1 hour ago, joe90 said:

Well that went well, Steamy Tea and me running round with joss sticks

There was not enough air being sucked in for me to smoke a fag.

The reason the chap gave about not doing instant results was that the house details (size basically) has to be entered into the software package.  As they were not available when Joe90 booked the test, he had to take a copy of the plans away.

I shall post up the loft hatch video as soon as I have uploaded it.

[SteamyTea]

Has anyone had trouble getting a video onto Youtube recently.

Uploaded it OK, but it has been stuck in processing, so uploaded again, same thing, and did the same this morning 

[Onoff]

52 minutes ago, SteamyTea said:

Has anyone had trouble getting a video onto Youtube recently.

Uploaded it OK, but it has been stuck in processing, so uploaded again, same thing, and did the same this morning 

 

Content filter's working as it should by the sounds of things!

 

?

[SteamyTea]

Could be, shall check how I spelt fan, may have added a y to the end.

[SteamyTea]

Think it has finally done what it is meant to do.  You have struggle to see the numbers.

 

[joe90]

Just got a call from the tester to say the result was 1.64, I am a bit  dissapointed considering other results on here, he did comment that apart from an ASHP pipe I forgot to seel, the leeks appeared to be shrinkage between wooden windows and brickwork/plaster which will be dealt with on redecorating once the place dries out completely. He also commented that when we opened the loft hatch (a warm roof) it made little difference which is not bad as sealing the loft is not an easy task. He did say he would return after I did remedial work if I wanted to but I don’t fancy forking out another £250 + VAT. I know it’s soo much better than most other houses (not the ones built by buildhub members ?).

[craig]

Don’t be too disheartened. 

 

I’ve been involved with certification and the builders have only achieved that figure. Even though they have on site training and everything else required.

 

That’s still a good result, not PH standard but you weren’t building to that level?

Edited May 21, 2019 by craig

[SteamyTea]

I wonder if that result takes into account that the pressure was at 60 Pa, rather than 50 Pa.

Considering that just about every window cill had a leak, I think that is alright.

There was also a leak by the WBS air inlet, forgot to mention that one.  But as you are probably going to change the pipe, it is not really an issue.

[Jeremy Harris]

Just a thought, but are we looking at different measurement units here?

 

The UK is a bit weird, in that our building regs don't use the near-standard air leakage/ventilation measurement system that pretty much everyone else in the world uses.  In particular, the standard expression for air leakage/ventilation rate in the passive house world is air changes per hour at 50 Pa pressure differential.  (ACH for short).  The UK building regs specify this in m³/m²/hour, where m³ is the air leakage and m² is the total internal wall/floor/ceiling/roof area at the location of the airtight layer.  The maximum allowable air leakage rate is 10m³/m²/hour.

 

There can be a difference between ACH and m³/m²/hr, depending on the design of the house.  For example, our air test was done by an Irish company, and they used the "normal" units, ACH at 50 Pa.  I then had to convert this to m³/m²/hr for building control.  Our ACH measurement was 0.49 ACH at 50 Pa, but the UK building regs figure was 0.6m³/m²/hr at 50 Pa.

[Gone West]

3 minutes ago, JSHarris said:

There can be a difference between ACH and m³/m²/hr, depending on the design of the house.  For example, our air test was done by an Irish company, and they used the "normal" units, ACH at 50 Pa.  I then had to convert this to m³/m²/hr for building control.  Our ACH measurement was 0.49 ACH at 50 Pa, but the UK building regs figure was 0.6m³/m²/hr at 50 Pa.

Strangely ours was exactly the same at 0.47, for both measurements, which surprised me.

[Jeremy Harris]

18 minutes ago, PeterStarck said:

Strangely ours was exactly the same at 0.47, for both measurements, which surprised me.

 

 

Interestingly, if we'd not had the tall vaulted ceilings upstairs, but had taken the airtight layer just behind conventional height ceilings, then our building regs figure would have increased to about 0.67 m³/m²/hr.  We had a measured air leakage volume at 50 Pa of 166m³/hr pressurised and 199m³/hr depressurised, so a mean of about 182.5m³/hr.

[joe90]

I will look at the doc when it arrives and report here (at least it’s not draughty ?)

[newhome]

9 minutes ago, joe90 said:

I will look at the doc when it arrives and report here (at least it’s not draughty ?)

 

I wouldn’t worry about it. You know there are a few areas where you can improve and you haven’t artificially lowered the result by sealing everything to within an inch of its life only to remove the sealing afterwards. If yours is a figure in ‘ordinary use’ what’s not to like? 

 

[lizzie]

@newhome exactly!  @joe90 if the testers had not temporarily taped up my gaps I would have had a poor result I’m sure.  They were tasked with achieving a result on the day and so they did all that temporary taping to get there. That was exactly my point last week.  Its such a shame after all your hard work. Maybe the paperwork will reveal an anomaly as suggested above.

[joe90]

In some ways I am pleased, the warm loft showed no particular problem and the biggest area to seal properly (all that expanding glue, OSB and expanding foam was worth the effort). As per another thread I did ask the plasterers to put a stop bead before the timber windows so I could mastic the join which would have been flexible but they argued it was not worth it, I DID know better. All window and door seals appear to work well so apart from waiting till the end of summer so any timber shrinkage has maxed out then I can caulk all timber/plaster joins. It did go through my mind that if I slightly over pressurise the house when I balance the MVHR then any leakage would be outward not inward????.

[jack]

30 minutes ago, joe90 said:

It did go through my mind that if I slightly over pressurise the house when I balance the MVHR then any leakage would be outward not inward????.

 

You'll be pushing warm moist air outwards, where it will condense at some point within whatever gaps it's moving through. Balanced pressure is better.

[gravelld]

That's why I don't like PIV.

[Mr Punter]

With @joe90's house does anyone know approximately what difference to annual running costs the difference between this test result and, say 0.6 would make? Does 1.0 really make much difference?

[joe90]

Just now, Mr Punter said:

With @joe90's house does anyone know approximately what difference to annual running costs the difference between this test result and, say 0.6 would make? Does 1.0 really make much difference?

 

Waiting with bated breath ?

[Ed Davies]

12 hours ago, SteamyTea said:

I wonder if that result takes into account that the pressure was at 60 Pa, rather than 50 Pa.

 

It should do. The standard way to do it is to measure the airflow at a range of positive and negative pressures and fit a formula then use that to work out the leakage at 50 Pa.

[Jeremy Harris]

7 minutes ago, Mr Punter said:

With @joe90's house does anyone know approximately what difference to annual running costs the difference between this test result and, say 0.6 would make? Does 1.0 really make much difference?

 

Probably very little, unless the house is in an exposed area. 

 

Although PHI set the air leakage rate at 0.6 ACH, and the target under building regs for a house with MVHR is 1m³/m²/hr, in reality I doubt that there's a massive benefit from getting much below about 1.5 ACH or so, especially if the house isn't in an exposed location. 

 

Wind seems to play a pretty significant part when it comes to heat loss, though, so any house in an exposed area is likely to have a higher heat loss than one in a sheltered area, and would probably benefit more from being well-sealed.  Where we are it's very sheltered, so I suspect it's debatable whether our low air leakage really makes a massive difference in practice.

[Jeremy Harris]

6 minutes ago, Ed Davies said:

 

It should do. The standard way to do it is to measure the airflow at a range of positive and negative pressures and fit a formula then use that to work out the leakage at 50 Pa.

 

This is the plot from our air test, with pressure differential (Pa) on the X axis and air leakage volume (m³) on the Y axis:

 

[joe90]

4 minutes ago, JSHarris said:

Wind seems to play a pretty significant part when it comes to heat loss,

 

Our site can be windy (today is no wind and scorching) and I realise “wind wash” can suck heat from a build. As the leakage is from places I can “correct” I am not too worried.