Insulated Slab Question

[Nickfromwales]

1 hour ago, Shaun McD said:

What type of DIY rig are you thinking? Your own blower? 

search on here, someone else was doing this with a car radiator fan jobby from a scrapyard.

[Sparrowhawk]

1 hour ago, Nickfromwales said:

I'm now going to get myself a DIY rig as suggested by others here, so I can perform my own "day of plugging / testing" on my clients behalf, eg before employing a 4rd party to come and test and issue a cert. Seems the best money my clients could spend, and is already going down well when I suggest it. 

 

1 hour ago, Shaun McD said:

What type of DIY rig are you thinking? Your own blower? 

This is my blower door that's awaiting commissioning. My house has 4 5 different doorway sizes so plan is to tape plastic sheet at the sides/tops to seal it in.

 

I am frustrated how oval the hole I cut in the door is. Am thinking of filling the gap or putting the fan in a tunnel (don't know what the technical term is) to guide the airflow.

[SteamyTea]

3 minutes ago, Sparrowhawk said:

I am frustrated how oval the hole I cut in the door is

Just tape it.

3 minutes ago, Sparrowhawk said:

don't know what the technical term is

Venturi, but that is when you want to get posh and measure pressure and flow as well.

 

[Nickfromwales]

8 minutes ago, Sparrowhawk said:

 

This is my blower door that's awaiting commissioning. My house has 4 5 different doorway sizes so plan is to tape plastic sheet at the sides/tops to seal it in.

 

I am frustrated how oval the hole I cut in the door is. Am thinking of filling the gap or putting the fan in a tunnel (don't know what the technical term is) to guide the airflow.

Use a builders flexi-tub bucket? Wedge that into the hole and tape, then push the fan into the bucket until snug.

 

Cut the bottom completely flush / out of the bucket, of course!

[Shaun McD]

18 minutes ago, SteamyTea said:

Same base.

PUR is shorthand for polyurethane.

PIR is shorthand for polyisocyanurate.

Polyurethanes often use isocyanurates as the hardening agent.

 

There is a difference, but only really in the manufacturing process of EPS (expanded) and XPS (extruded).

 

It is the thermal and mechanical properties that are important.

 

Can you help me understand what the different properties would be for my application and what the impact of choosing either would be? It will be fixed to the inside of the stud, with joints taped to act as vapor and airtight layer, batten added for service cavity before plasterboard.

 

5 minutes ago, Sparrowhawk said:

 

This is my blower door that's awaiting commissioning. My house has 4 5 different doorway sizes so plan is to tape plastic sheet at the sides/tops to seal it in.

 

I am frustrated how oval the hole I cut in the door is. Am thinking of filling the gap or putting the fan in a tunnel (don't know what the technical term is) to guide the airflow.

 

This is super interesting and seems right up my street ha! I was only ever involved in a test once, and the tester was more keen to get job done and out rather than answer any questions. I remember he had smoke candles to see leakage points, is this still the method? Im guessing it is easiest to pressurize the room to test on this kind of level? 

Pretty sure I have an old radiator fan and a washing machine motor kicking about to rig something up!

[Nickfromwales]

5 minutes ago, Shaun McD said:

I remember he had smoke candles to see leakage points, is this still the method?

Maybe...

 

https://www.toolstation.com/smoke-pellets/p38123?store=W8&utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&mkwid=_dc&pcrid=&pkw=&pmt=&gclid=CjwKCAiAl9efBhAkEiwA4ToriuY-AcXOHK9G3nIStFhy-s13nL9thMMcGEGfjru1uSsANb6VERbOiRoCe8oQAvD_BwE&gclsrc=aw.ds

 

These burn / output smoke for a good while, but you need to see if they'll kill you ( or not )  

[Sparrowhawk]

5 minutes ago, Shaun McD said:

This is super interesting and seems right up my street ha! I was only ever involved in a test once, and the tester was more keen to get job done and out rather than answer any questions. I remember he had smoke candles to see leakage points, is this still the method? Im guessing it is easiest to pressurize the room to test on this kind of level? 

Pretty sure I have an old radiator fan and a washing machine motor kicking about to rig something up!

My house is so draughty that yes I'm planning to depressurise a room at a time to start with. I do have a second fan so if I need more oomph I can mount two in the door.

 

Why a door? This was free and wood's expensive at the moment. Old doors are also cheap on FB Marketplace.

[Nickfromwales]

20 minutes ago, Sparrowhawk said:

My house has 4 5 different doorway sizes so plan is to tape plastic sheet at the sides/tops to seal it in.

I believe you only install the "blower" into a front, side / rear doorway and thus pressurise the whole house. Are you thinking of doing room by room?  

[Shaun McD]

1 minute ago, Sparrowhawk said:

My house is so draughty that yes I'm planning to depressurise a room at a time to start with. I do have a second fan so if I need more oomph I can mount two in the door.

 

Why a door? This was free and wood's expensive at the moment. Old doors are also cheap on FB Marketplace.

 

So depressurize instead of pressurize? The previous one I seen done must have been pressurized as we walked around with the candles and you could see the junctions in which air was getting forced out as that is where the smoke was pulled to. I suppose in a depressurized test you do the same thing but the air will be blowing away from the leakage point, so maybe its no difference. 

A door makes sense yeah, fan needs to be securely mounted for obvious reasons. I am a few months away from having rooms to test but for sure this will be something to do, provided i dont get a great result from the TF company first time ha!

[Shaun McD]

7 minutes ago, Nickfromwales said:

I believe you only install the "blower" into a front, side / rear doorway and thus pressurise the whole house. Are you thinking of doing room by room?  

 

I was thinking on a room by room approach too, would reduce the volume of air to move through the fan, and would think it be more manageable sizes for a novice tester? My better half reminds me my time is not worth much so...

[Nickfromwales]

Just now, Shaun McD said:

 

I was thinking on a room by room approach too, would reduce the volume of air to move through the fan, and would think it be more manageable sizes for a novice tester? My better half reminds me my time is not worth much so...

You still test room by room, but with the whole house pressurised.

You're not looking to replicate Michael Jackson's "oxygen tent of eternity", so going full bore in each room may be a bit OTT?

 

All I need now is somebody cleverer than me to tell me how to gauge the ACH from the DIY rig.

 

The winner gets a half-eaten Greggs steak bake. Only been in the van for 2 days, still good.

[Thorfun]

18 minutes ago, Shaun McD said:

It will be fixed to the inside of the stud, with joints taped to act as vapor and airtight layer, batten added for service cavity before plasterboard.

hey, this comment has me a bit worried and maybe someone else who knows more than me can comment. but even though taped PIR/PUR may act as a reasonable air tight barrier i don't think it's a vapour control layer. most people seem to use a specific AVCL membrane or some TF companies use airtight OSB (i believe it's called propassiv iirc).

 

@SteamyTea is a smart cookie and might know how good PIR is as a VCL.

[jack]

8 minutes ago, Shaun McD said:

So depressurize instead of pressurize?

Just FYI, the formal test involves taking an average of pressurisation and depressurisation.

[Nickfromwales]

4 minutes ago, jack said:

Just FYI, the formal test involves taking an average of pressurisation and depressurisation.

Yup, 10 pos and 10 neg iirc.

[Sparrowhawk]

11 minutes ago, Shaun McD said:

 

So depressurize instead of pressurize?

If I depressurise I can feel the draughts with my hands. If using smoke I might pressurise.

 

6 minutes ago, Nickfromwales said:

All I need now is somebody cleverer than me to tell me how to gauge the ACH from the DIY rig.

Yes that is the million dollar question.

 

I've found https://www.builditsolar.com/Projects/Conservation/BlowerDoor/FlowRates.htm but not gone into the details yet.

 

Checking if I reach 50Pa should be simple(!) with a U-shaped tube through the door, fill it with coloured water and measure the height change.

Volume of air shifted - well Screfix are out by a factor of 10 in their quoted l/s for this fan so no idea.

[Shaun McD]

3 minutes ago, Thorfun said:

hey, this comment has me a bit worried and maybe someone else who knows more than me can comment. but even though taped PIR/PUR may act as a reasonable air tight barrier i don't think it's a vapour control layer. most people seem to use a specific AVCL membrane or some TF companies use airtight OSB (i believe it's called propassiv iirc).

 

@SteamyTea is a smart cookie and might know how good PIR is as a VCL.

 

Had me worried too, it seems much more normal to be adding the VCL (Pro Clima Intello etc.) between the stud and the PUR/PIR layer.

However, to their credit, our TF company has spent considerable time talking to me on this point. 

They do not use an OSB racking board for example, instead its a breathable board, the specific one escapes me but something like Elka Strong board.

The logic is all around interstitial condensation, and that in their view, the VCL inside the insulation is incorrectly used, or at least not required.

TBH the science, or potential lack of, goes over my head but I have some level of confidence that the TF company AT LEAST believe what they are doing is best, i am just not the person to know if its wrong!

Looking forward to having the forum either support the idea, or have me now thinking il need a new TF company ha

[SteamyTea]

32 minutes ago, Shaun McD said:

Can you help me understand what the different properties would be for my application and what the impact of choosing either would be

There are 4 main parameters:

Thermal Conductivity, the W.m^-1.K^-1

The Compression Strength, the MPa

The Vapour Resistance, the gm/MNs

The Moisture Absorption, usually as a percentage, %

 

There are secondary considerations, price, handleability, fire resistance, chemical reactions (polystyrene and PVC don't mix well), sound absorption/transmission.

 

The manufacture should have al those details, even if they do not publish them on the specification data sheet.

[SteamyTea]

22 minutes ago, Nickfromwales said:

All I need now is somebody cleverer than me to tell me how to gauge the ACH from the DIY rig.

Not easy, but an inclined manometer and a flow meter will be needed.

All the things that a plumber probably has already.

[Shaun McD]

9 minutes ago, SteamyTea said:

There are 4 main parameters:

Thermal Conductivity, the W.m^-1.K^-1

The Compression Strength, the MPa

The Vapour Resistance, the gm/MNs

The Moisture Absorption, usually as a percentage, %

 

There are secondary considerations, price, handleability, fire resistance, chemical reactions (polystyrene and PVC don't mix well), sound absorption/transmission.

 

The manufacture should have al those details, even if they do not publish them on the specification data sheet.

 

Thanks for this, is there a reputable 70mm board that I could reference as an acceptable benchmark, that i can compare the board used by the TF company against?

[SteamyTea]

2 minutes ago, Shaun McD said:

is there a reputable 70mm board that I could reference as an acceptable benchmark

Pick Celotex or Kingspan as the benchmarks, they are well known and available almost everywhere.

 

Similar to comparing all cars to a Ford.

Edited February 22, 2023 by SteamyTea

[Shaun McD]

8 minutes ago, SteamyTea said:

Pick Celotex or Kingspan as the benchmarks, they are well known and available almost everywhere.

 

Similar to comparing all cars to a Ford.

 

Ok sounds good, so use the like of a kooltherm K12 as the benchmark and forget about pur v pir?

[SteamyTea]

8 minutes ago, Shaun McD said:

 

Ok sounds good, so use the like of a kooltherm K12 as the benchmark and forget about pur v pir?

Yes, good start.

[Shaun McD]

9 minutes ago, SteamyTea said:

Yes, good start.

 

Thank you very much for the guidance, greatly appreciated!

[Thorfun]

54 minutes ago, Shaun McD said:

 

Had me worried too, it seems much more normal to be adding the VCL (Pro Clima Intello etc.) between the stud and the PUR/PIR layer.

However, to their credit, our TF company has spent considerable time talking to me on this point. 

They do not use an OSB racking board for example, instead its a breathable board, the specific one escapes me but something like Elka Strong board.

The logic is all around interstitial condensation, and that in their view, the VCL inside the insulation is incorrectly used, or at least not required.

TBH the science, or potential lack of, goes over my head but I have some level of confidence that the TF company AT LEAST believe what they are doing is best, i am just not the person to know if its wrong!

Looking forward to having the forum either support the idea, or have me now thinking il need a new TF company ha

my Intello Plus is inside of ALL the insulation. i fitted 140mm glass wool between the studs, 80mm PIR on top of the studs, then my AVCL membrane, followed by a 25mm service cavity.

 

i don't recall reading a single self-build on here where they didn't have some form of VCL membrane internally to the insulation. even if that was simple plastic sheeting.

 

i'm a cynical ******* and so i'm thinking that a company might say anything to save some money and not have to install a physical membrane! maybe post a question in the relevant forum on this subject? or do a quick search to see if anyone else has done it.

[Shaun McD]

6 minutes ago, Thorfun said:

my Intello Plus is inside of ALL the insulation. i fitted 140mm glass wool between the studs, 80mm PIR on top of the studs, then my AVCL membrane, followed by a 25mm service cavity.

 

i don't recall reading a single self-build on here where they didn't have some form of VCL membrane internally to the insulation. even if that was simple plastic sheeting.

 

i'm a cynical ******* and so i'm thinking that a company might say anything to save some money and not have to install a physical membrane! maybe post a question in the relevant forum on this subject? or do a quick search to see if anyone else has done it.

 

I would be quite cynical about these things too ha, and they do add the VCL layer to flat ceilings for example. I am sure they will have no issue (just an extra cost) to install the membrane on top of insulation, but they are adamant it is not needed due to their use of the breathable racking board on the outside, hopefully someone on here is more informed and can confirm or deny the validity!