Live self-Builds - mod warning in post no. 1

just do it

Jalopy81 wrote: »

Hi All.
New to posting on boards but have been lurking around this forum for a few years particularly about airtightness. Just got test done and come back at 1.3 ach on a block built house.
Just thought I'd return some of the knowledge gained here. I have taken loads of photos during construction so if I can help anybody during the long hours of origami folding tapes and membranes just let me know

Welcome Jalopy. Are you happy with that result? Sounds like you did it yourself

Jalopy81

Did it myself through the dark winter nights. The actual number is closer to 1. Was pushed to get the Certs out for building control so there was some remedial done afterwards. The spark had left big holes at 2 of the ceiling roses and I still had a few conduits to cap at the eaves which were hard to get to.
Other biggest issue was where the MHRV passed the membrane in the ceiling and a few rogue screws when fixing the insulated plasterboard. Wasn't aiming for passive but close to it so I am quite happy with it.

just do it

It's a great result alright, fair deuce to you

stickybookmark

just do it wrote: »

Best of luck with the build. What's the detail? Foundation, walls, windows etc

-Normal strip foundations.
-I'm having block walls internally throughout the whole house.
-Concrete slab 1st floor
- Aiming for a BER of A2 with the following combination: Ground Source Heat Pump/Wall u-value 0.2W/m2k/Mechanical Ventilation with Heat Recovery(MVHR)/Wood Burning Stove
-double glazed windows haven't decided on material/style yet
- windows to have U value of 1.2
- doors to have U value of 1.8
- 6 inch cavity filled with beeds
- 150mm insulation in the floor of the ground floor
- no insulation in the first floor floor (builder told me this isn't necessary when already have concrete slab)
- 50mm insulated plaster board on the inside of all external walls
- Attic to be used for storage so putting insulation in the pitched roof
-still deciding on doors but probably a hardwood front door and maybe composite back doors

hexosan

Triple glazing is very little extra compared to double. If it were me I'd scrap the insulated plasterboard slab as it's just a bad detail with a new build (there a ton of threads and posts on this) I'd increase the cavity to 200mm and pump with bead. This will work out cheaper than 150mm bead + 38mm slabs.

lownhard

hexosan wrote: »

Triple glazing is very little extra compared to double. If it were me I'd scrap the insulated plasterboard slab as it's just a bad detail with a new build (there a ton of threads and posts on this) I'd increase the cavity to 200mm and pump with bead. This will work out cheaper than 150mm bead + 38mm slabs.

Plus one on this.

Why separate the insulation layers other than to satisfy the "that's the way we do it in dormer bungalow land" brigade? One wider cavity - perhaps try and increase cavity to 250mm. That is what I am currently building. Bit of detailing around opes, but very manageable for willing builder.

Can be difficult to get a good u-value on a warm roof. I am getting a truss roof with 222mm rafters. Have decided to add 75mm external PIR and and 50/100mm service cavity to boost insulation in this area. Also using a quality product like Metac as opposed to cheaper mineral wool between the rafters will help boost performance.

Be sure to read all the threads on here about making block built houses airtight around precast floor, wall chases, wall floor junctions, scratch coating external facing walls etc

You have lots of research to do...enjoy it!

Have you done a cost benefit on GSHP versus alternatives (ASHP or a solid fuel boiler). All that digging/boring....and the cost of running the pump. This is assuming you do not have access to mains gas. Fclauson on here has done some good analysis with his combo of ASHP and PV solar (although unfortunately no longer able to sell electricity back to the grid)

stickybookmark

hexosan wrote: »

Triple glazing is very little extra compared to double. If it were me I'd scrap the insulated plasterboard slab as it's just a bad detail with a new build (there a ton of threads and posts on this) I'd increase the cavity to 200mm and pump with bead. This will work out cheaper than 150mm bead + 38mm slabs.

Do you work for my builder?! :P:PThat's exactly what they tried to get us to do but we didn't go for it.
My engineer had concerns about increasing the cavity to 200mm. Something to do with the inner leaf being so far from the outer leaf that it was then no longer considered part of the same wall or something? I'll have to look up old emails.

sydthebeat

stickybookmark wrote: »

Do you work for my builder?! :P:PThat's exactly what they tried to get us to do but we didn't go for it.
My engineer had concerns about increasing the cavity to 200mm. Something to do with the inner leaf being so far from the outer leaf that it was then no longer considered part of the same wall or something? I'll have to look up old emails.

Sounds like an old engineer unwilling to learn new processes.

There have been cavities constructed that are 300mm wide.

stickybookmark

lownhard wrote: »

Have you done a cost benefit on GSHP versus alternatives (ASHP or a solid fuel boiler). All that digging/boring....and the cost of running the pump. This is assuming you do not have access to mains gas. Fclauson on here has done some good analysis with his combo of ASHP and PV solar (although unfortunately no longer able to sell electricity back to the grid)

As well as the fact it's more efficient than Air to Water, I prefer the fact that GSHP is more weather/climate change proof. We had the soil tested and it's very suitable for geothermal as well. Planning to run it on night-rate electricity and not run it at all during the day which you couldn't do with ASHP.

lownhard

stickybookmark wrote: »

Do you work for my builder?! :P:PThat's exactly what they tried to get us to do but we didn't go for it.
My engineer had concerns about increasing the cavity to 200mm. Something to do with the inner leaf being so far from the outer leaf that it was then no longer considered part of the same wall or something? I'll have to look up old emails.

Have you an architect on board to deal with thermal performance or is your (old school) engineer dictating all aspects?

http://www.vartryengineering.com/products/extra-long-wall-tie-large-cavities.html

hexosan

stickybookmark wrote: »

Do you work for my builder?! :P:PThat's exactly what they tried to get us to do but we didn't go for it.
My engineer had concerns about increasing the cavity to 200mm. Something to do with the inner leaf being so far from the outer leaf that it was then no longer considered part of the same wall or something? I'll have to look up old emails.

Get a new engineer he hasn't a clue. I built a 250mm cavity that's when you run into structural issues. (Which are easily addressed) If Id my time back again Id just do a 200mm cavity.

Tell your engineer there's cavity ties made by Vartry engineering in wicklow for 200 & 2500mm cavities.

stickybookmark

lownhard wrote: »

Have you an architect on board to deal with thermal performance or is your (old school) engineer dictating all aspects?

http://www.vartryengineering.com/products/extra-long-wall-tie-large-cavities.html

No strangely enough after I pay the builder and the assigned certifier (the engineer) there's not much spare change left to pay for an architect on top of that

An Arch Tech designed my house (pre-Bcar) but he is no more use to me as he can't certify so he's not involved anymore

just do it

+1 on wide cavity. All that's required is a few extra longer wall ties.

I've seen a few cases of mould behind insulated plasterboard. No thank you for me sir!

BarneyMc

stickybookmark wrote: »

Planning to run it on night-rate electricity and not run it at all during the day which you couldn't do with ASHP.

Why not?

stickybookmark

lownhard wrote: »

Can be difficult to get a good u-value on a warm roof. I am getting a truss roof with 222mm rafters. Have decided to add 75mm external PIR and and 50/100mm service cavity to boost insulation in this area. Also using a quality product like Metac as opposed to cheaper mineral wool between the rafters will help boost performance.

)

Only getting my head around this stuff but with a truss roof on your house doesn't that mean you can't use your attic for storage or a games room etc. So why is it worth spending money on insulating the pitched roof then?

150mm TP10 + 82.5MM Kingspan K18 is what the BER assessment calls for in my pitched roof - insulated on rafter

stickybookmark

BarneyMc wrote: »

Why not?

Doesn't ASHP run on taking heat from the warm air outside and heating your house with it? I assume at night time when air is cold wouldn't be a good time to be running it? I'm not sure but based on my understanding of it...

JimmyMW

stickybookmark wrote: »

Doesn't ASHP run on taking heat from the warm air outside and heating your house with it? I assume at night time when air is cold wouldn't be a good time to be running it? I'm not sure but based on my understanding of it...

Sorry I mis read your mail, basically the the ASHP would have to work harder to extract the available heat in the air, some have a pre heater.

just do it

Stickybookmark

Have you looked into PV panels to satisfy Part L rather than a HP? Also have you an airtightness target and detail to eliminate thermal bridges?

Now's the time.....

BryanF

stickybookmark wrote: »

150mm TP10 + 82.5MM Kingspan K18 is what the BER assessment calls for in my pitched roof - insulated on rafter

What depth is the joist? I'd put the insulation boards outside the vapour barrier and just have an empty service cavity inside, or if your not getting spots maybe just vapour barrier then plasterboard. Your arch/arch tech should be specifying the roof build-up. The VB doubles as an air-tightness membrane so all gaps etc are taped and sealed to walls etc.

lownhard

stickybookmark wrote: »

-Normal strip foundations.
-I'm having block walls internally throughout the whole house.
-Concrete slab 1st floor
- Aiming for a BER of A2 with the following combination: Ground Source Heat Pump/Wall u-value 0.2W/m2k/Mechanical Ventilation with Heat Recovery(MVHR)/Wood Burning Stove
-double glazed windows haven't decided on material/style yet
- windows to have U value of 1.2
- doors to have U value of 1.8
- 6 inch cavity filled with beeds
- 150mm insulation in the floor of the ground floor
- no insulation in the first floor floor (builder told me this isn't necessary when already have concrete slab)
- 50mm insulated plaster board on the inside of all external walls
- Attic to be used for storage so putting insulation in the pitched roof
-still deciding on doors but probably a hardwood front door and maybe composite back doors

We're all on a budget and everyone is sharing experiences. My engineer hasn't much interest in insulation/airtightness, but has been great on the structural stuff. Perhaps you might consider an energy consultant to help you with detailing. Some stuff on this site to whet the appetite http://passivedesign.org/

You need someone who is not just concerned with "doing it they way we have always done it"

You can get "attic trusses" that allow for usable space (maybe even habitable space).

BTW using a heat pump will lend to UFH upstairs but that will require min 25mm of insulation on top of the slab.

Because you are using a slab in your construction drawings I would allow 100mm on top of slab/200mm slab/200mm service cavity below slab. Basically allow min 500mm between GF ceiling and finsihed floor level on the FF.

Cavanjack

893bet wrote: »

Starting to come together.

Hoping to start elextrical second fix next week and plumbing second fix to follow!

Looking good. Ready to start plastering myself now. Did you put air tight tape between floor and walls? Is it common practice for the plaster to be finished so far from the floor?

893bet

Cavanjack wrote: »

Looking good. Ready to start plastering myself now. Did you put air tight tape between floor and walls? Is it common practice for the plaster to be finished so far from the floor?

I am waiting for an Airtightness test to see how much leakage is at this junction. If there is a significant amount I will taping also.

That is common as the skirting will be covering. The sand and cement coat went all the way down.

BarneyMc

893bet wrote: »

Starting to come together.

Hoping to start elextrical second fix next week and plumbing second fix to follow!

The middle image shows some sort of hood for the stove? Can I ask what this is for?

893bet

BarneyMc wrote: »

The middle image shows some sort of hood for the stove? Can I ask what this is for?

I installed a poujoulat chimney system. See below link and some attached pics.

http://www.poujoulat.co.uk/produit/9/17/1/twin-wall-insulated-chimney-system/therminox-ti-zi.html

Its a fab system but if I could go back i would have installed standard block chimneys

893bet

Just had my first Airtightness test.

Air permability 2.65 m3/hr/m2
Air change per hr 2.34

Very happy with that given that there are still several weak points in the house yet to be addressed and the fact that I did all the Airtightness detailing myself! Had visions of an 8.4 or worse.

sydthebeat

893bet wrote: »

Just had my first Airtightness test.

Air permability 2.65 m3/hr/m2
Air change per hr 2.34

Very happy with that given that there are still several weak points in the house yet to be addressed and the fact that I did all the Airtightness detailing myself! Had visions of an 8.4 or worse.

Air change per hour is approx 'air permability divided by 20'

How did you tester calculate the ac/hr )

893bet

sydthebeat wrote: »

Air change per hour is approx 'air permability divided by 20'

How did you tester calculate the ac/hr )

I have no idea and may have gotten mixed up in the results and units. The 2.65 is correct as this is the one we spoke at length about. Should be able to get well below 2 for final test which I will be happy with.

sydthebeat

I think he's probably given you the q50 and n50 figures.

For your final Ber cert your assessor will divide the q50 by 20 for the air changes per hour figure.

stickybookmark

just do it wrote: »

Stickybookmark

Have you looked into PV panels to satisfy Part L rather than a HP? Also have you an airtightness target and detail to eliminate thermal bridges?

Now's the time.....

Thanks. I'm not having HP to satisfy part L. I'm having it coz I want to heat my house cheaply!

Don't know what the air tightness target is, will check. I know the builder is going to do a test at the end though.

Thermal bridges - quinnlite blocks are going on top of the deadwork at the thermal bridge. These were delivered this morning actually glad to know I'm doing my bit to pay IBRC's bad debts :pac::pac:

And there's goign to be a tape/membrane put around teh windows (right to the outside of the opening) to seal them, that's for air tightness as well

stickybookmark

lownhard wrote: »

BTW using a heat pump will lend to UFH upstairs but that will require min 25mm of insulation on top of the slab.

Because you are using a slab in your construction drawings I would allow 100mm on top of slab/200mm slab/200mm service cavity below slab. Basically allow min 500mm between GF ceiling and finsihed floor level on the FF.

Hmm...I only have 150mm service cavity in the GF ceiling/FF floor.
This has to take the HRV ducting and allow a slope for foul pipes.
This was deemed to be enough by project manager/engineer will revisit.
Only thing is a good bit of height has been taken off my rooms already from the original plans, don't really wanna take any more off unless I absolutely have to.

I've never heard this in bold. I had insulation in the GF ceiling/FF floor and the builder insisted, and I mean insisted on taking it out coz waste of money when you have a concrete slap first floor. I asked my bro who has a concrete slab FF (and UF heating incidentally) and he said correct you don't need insulation for noise when you have a concrete slab first floor. But you're right any photos I've seen the UF heating pipes are placed on the insulation so wonder how they're gonna place them on the FF floor...