HRV system with Block Cavity Worthwhile?

Villain

Well my selfbuild in underway and after looking at various ICF and timber frame systems I have decided to go with the traditional Block Cavity. I'm hoping to get the foundations in before xmas at least and possibly the footings.

I have always liked the idea of a HRV system especially when used with the ICF system however is it worth while putting a HRV system into a block cavity structure or will it be just too hard to get it air tight?

sinnerboy

Irish1 - you can acheive air tightness - go here and download the relevant guidinace for you chosen wall type

http://www.planningportal.gov.uk/england/professionals/en/1115314255826.html

Best not to include an open fire however .

AND

Give serious consideration to ICF - not too late . Far better job

ardara1

Block construction average air permeablity of 6 (10 max allowable) - aim for below 4 to make HRV worth while - if you don't achieve it - don't do it. It's easily achieved and the only cost is time taking care on site. ICF is great at sealing 4 corners - but air leakage is predominantly in other areas, around penetrations, meter boxes, loft hatches, window surrounds - and even worse - openings in windows. Search you tube for tests- air tightness Ireland have a video up there of one being down - they'll give you good advice over the phone also

ardara1

sinnerboy wrote: »

Irish1 - you can acheive air tightness - go here and download the relevant guidinace for you chosen wall type

http://www.planningportal.gov.uk/england/professionals/en/1115314255826.html

Best not to include an open fire however .

AND

Give serious consideration to ICF - not too late . Far better job

Sinner - do you owe me a pint?

Villain

cheers lads, time and effort won't be an issue but knowledge may well be. sinnerboy I have no doubts that ICF is an excellent product when done correctly however the costs and lack of local experience don't make it sensible for me. The external finish is too expensive for what it is.

Builderfromhell

Excuse my ignorance. What's ICF?

Villain

Insulated Concrete Form, google it and you will find loads of info.

ardara1

Builderfromhell wrote: »

Excuse my ignorance. What's ICF?

Insulated Concrete Form - lego blocks infilled with poured concrete

irish1

irish1 wrote: »

cheers lads, time and effort won't be an issue but knowledge may well be. sinnerboy I have no doubts that ICF is an excellent product when done correctly however the costs and lack of local experience don't make it sensible for me. The external finish is too expensive for what it is.

I used ICF, I erected it myself. Lot of hard work but not nearly as skilled as blocklaying etc. Detailing around opes, ceiling fixtures, services etc are very important from an air tightness view point, I may get one done just to check for weaknesses & rectfy. HRV is working well, but a bit dissapointed with the airtightness of the windows & doors, it's possible to hear through some of the frames (can't feel a draught but can hear sound by some of the openers).

As for external finish I used conventional sand/white cement on expanded mesh. Looks as good as any concrete house now.

muffler

Builderfromhell wrote: »

Excuse my ignorance. What's ICF?

What did you post in another thread - you are an architect/builder.

Excuse my ignorance but who is taking the michael here

sunnysoutheast

aarrrgh second time I've had to type this!

We have a block-built house and HRV, with skimmed insulated p'board to external walls. Take care around opes. etc. but that'd good practice anyway.

Make sure your HRV system has "overboost" for bathrooms and clear it with whoever is certifying the build that you can get rid of those holes in the wall and tricklevents. You'll still need kitchen extraction.

We've been in a few weeks now and have noticed no condensation etc. on the windows, in marked contrast to the estate-built house we used to live in.

PM me if you want any details.

SSE

sinnerboy

ardara1 wrote: »

Sinner - do you owe me a pint?

I guess so - see you at IIE later ?

sinnerboy

irish1 wrote: »

cheers lads, time and effort won't be an issue but knowledge may well be. sinnerboy I have no doubts that ICF is an excellent product when done correctly however the costs and lack of local experience don't make it sensible for me. The external finish is too expensive for what it is.

Please think again . I spoke with 2 ICF system providers at Plan Expo last week .
They will either train you up at therir place or "lend" you a guy to "hand hold" as long as necessary .

Villain

SunnySouth East what boards did you use on the external walls and what type of plaster mix?

sas

sinnerboy wrote: »

Please think again .

Why? What's your particular love of ICF?

sunnysoutheast

hi irish1

The boards were the 37mm (I think) xtratherm foil-backed ones. Don't know what sort of plaster it was. The main complication was cutting the holes for sockets etc. and we've got a bit of making good to do.

As a suggestion to the mods can we have sticky "the best method of building is...." thread where whomsoever wants to can argue the "ICF vs. T/frame vs. block vs. Poroton vs. wattle-and-daub" debates until the cows come home. I think too many threads on here go off-topic into a debate between people with vested interests. People who are just trying to share experiences of navigating through the building maze can just ignore it.

SSE

sinnerboy

sas wrote: »

Why? What's your particular love of ICF?

OP was considering ICF . Haven't used it yet myself ,I should declare this , so no "particular love" .

It offers a much better chance of actually obtaining in reality the thermal performance that cavity walls often do not . Badly installed cavity insulation can lead to an actual under performance.

Timber frame or Poroton will also tend to perform better . I say "tend" becuase badly built work will not perform no matter what system .

Eco developer

Hi irish1,

cavity block is capable of delivering an airtight building envelope (go for a 6 inch cavity with Ecobead). However, it is quite a challenge to get good levels of airtightness. We have achieved less that 3 air changes per hour @ 50Pa on a blower dower test (and hope to do better in future). You need to research airtight membranes, tapes and seals. The materials are relatively cheap when you consider how much it can improve the performance of the house !!! There are new companies coming in to fill this void in Ireland. <SNIP> is already established and firms such as <SNIP> are getting a toe hold in Ireland.

The key to success is 'no gaps'. All building fabric penetrations (waste pipes etc) must be fully sealed. As do light fittings, sockets, window perimeters and attic doors. Forget about recessed lights on the first floor ceiling. To get best results a sealed fire with a balanced flue will prevent any heat loss up the chimney. Also, you will need to make the joists airtight !

This is a huge area and deserves much more attention. I believe that after orientation and insulation, airtightness is the most important factor in building performance. This is something that the Irish building industry will have to get to grips with from now on.

Edit by muffler: First post and we immediately mention a company name and what it does. Red card.

sinnerboy

sinnerboy wrote: »

Please think again . I spoke with 2 ICF system providers at Plan Expo last week .
They will either train you up at therir place or "lend" you a guy to "hand hold" as long as necessary .

I had the same offer and the guy was on site to help me fit the gable ends.
Very useful.

bakerbhoy

Looking for advice on maximising airtightness in the ceiling of bungalow.I will be slabbing with insulated plasterboard and either rigid between joists or rockwool between and over.Do i need to add a membrane to either mix.
I'm clear enough about walls, windows ,services etc from previous threads/ posts.:cool:

bakerbhoy

bakerbhoy wrote: »

Looking for advice on maximising airtightness in the ceiling of bungalow.I will be slabbing with insulated plasterboard and either rigid between joists or rockwool between and over.Do i need to add a membrane to either mix.
I'm clear enough about walls, windows ,services etc from previous threads/ posts.:cool:

I added a membrane to the ceiling joists before counter battons and taped it to the wall to ensure air tightness.