Creating a breathable build

Prodigalson

All help or suggestions welcome as I’ve spent so many hours reading the boards and another Irish construction forum at this stage I’m lost with the different options.

We’re deciding on the type of construction for our dormer with attached garage.

Will use natural breathable materials where the budget allows

The general overview.

Timber frame is preferred choice but not sure if budget will allow, currently waiting on quotes.
Would an air tight SIP build be viable with only window trickle vents? Would a breathable structure decrease the possible condensation issues? My other half is totally against a HRV.

•Foundation for TF or Concrete
Insulated/Passive foundation or best option for traditional foundation with lightweight blocks to help lessen cold bridging, anyone with experience with this? Lightweight blocks below DPC? Some manufactures claim there products as suitable.

•Walls
External insulation not an option for us as this stage we’re done to far with planning.

Cavity wall Inner leaf light block plastered with a breathable plaster. Is there an issues running service with this method? Are aerated blocks to brittle when hanging fixtures at a later date?
A 150 Cavity with a breathable material? full fill pumpbed or Suggestions please, an Irish manufacture has a 140 ridged board that only requires 10mm clearance,would this be a more breathable option than other rigid boards even with its cold bridging potential,If a good u-value is not achievable with this method is it a waste of time to mix the ridged cavity insulation with aerated block and breathable plaster.
Dense block external wall

•Roof Insulated with Cellulose


UFH both floors
Structural timer first floor with a screed poured for UFH and noise reduction.
Condensing oil boiler for now but will leave accesses for Ground/Air heat source at a later date,2 small wood burning stoves with exposed room flue to take any heat advantages possible.
Solar panels & will be looking at harvesting rain water for garden or possibly sanitary.

Finally anyone a recommendation for a good BER/DEAP/PHPP in Kildare/Dublin and a rough price for the
service.

Sorry it’s so long winded.

sydthebeat

prodigalson...

breathable construction is required where the structure of the building requires it. In general that would include most timber frames, or natural build methods such as straw bale, cob etc, or sometimes in single leaf block builds.

when building with concrete block in a double leaf situation the requirement for 'breathability' is diminished greatly, to the point at which its negligible.

Prodigalson

Thanks Syd
What would your opinion be on a SIP without HRV,would there be a long risk for timber decay or possibly have window condensation issues.

With double leaf build is using Light weight block still an advantage in terms of time to heat the building and with insulation would it be better just just go ridged boards in the attic as well rather than Cellulose?

imitation

I think your best bet is to sell HRV to your OH or go with a standard build. An airtight house without HRV sounds like a nightmare, you`d have condensation issues along with stuffiness, it would be uncomfortable and unhealthy. Everything I have seen of HRV is good, it`ll provide consistent ventilation where vents and other methods depend on how the wind is blowing. I think that combined with air quality and heat savings make it an easy sell to me.

Prodigalson

imitation

HRV does seems to be the way forward but I have read a few debates on an Irish construction forum regarding improper installation and health issues in cases where the building becomes sick and HRV spreads the problem to all areas,which is my OH concern,we've a a baby on the way so its a worry to get ventilation correct.

A friend had HRV installed about 2 years ago,timber frame house not a high spec in terms of insulation and finds it a real oil saver and very comfortable to live in with that fresh air feeling,might have to drop over for a visit.

In terms of installation issues we visited two friends last year that had GSHP installed and both houses were cold with high electric bills while another friend put his GSHP in end of last year ,better installer and went bore hole rather than on the flat and its brilliant,running cost fine and nice level of heat.
HRV I'm sure will be the same if installed correctly and the building is in good health its a winner.

imitation

Prodigalson wrote: »

imitation

HRV does seems to be the way forward but I have read a few debates on an Irish construction forum regarding improper installation and health issues in cases where the building becomes sick and HRV spreads the problem to all areas,which is my OH concern,we've a a baby on the way so its a worry to get ventilation correct.

In terms of installation issues we visited two friends last year that had GSHP installed and both houses were cold with high electric bills while another friend put his GSHP in end of last year ,better installer and went bore hole rather than on the flat and its brilliant,running cost fine and nice level of heat.
HRV I'm sure will be the same if installed correctly and the building is in good health its a winner.

I would be more concerned by mould and condensation caused by improper ventilation without a HRV than potential HRV problems. Getting it installed correctly is always a worry, but if you go with a reputable supplier it should hopefully be ok. My builder has offered to do it, and I think it maybe a good solution, if anything becomes apparent before the final snagging I can take him to task on it. I have heard of installers who are gone like a shot once the system is installed and they are paid.

Prodigalson

Full agreement,good luck with the build and HRV,you've researched yourself I'm sure but here's something I came across on another forum worth a read,will pm you the link it's a good discussion with some useful links here's an extract...you may have seen it all before.

"Flexible ducting not recommended, less efficient, more places for condensation and dirt to get trapped. So make sure rigid ducting is specified.

If you look up sap Appendix Q, you will see that they state that the efficiency of the units is only valid for rigid ducting. The Appendix Q rating is the efficiency rating used in BER certs so ensure the unit you getting installed is rated if you are concerned about having it's efficiency reflected in your cert.

All pipes should be insulated, especially in attic, where temperature difference can lead to condensation if they are not adequately insulated, also the heat would be lost to your attic space instead of finding it's way back to the heat exchanger in the MHVR.

Get quotes from a number of suppliers so you can compare.

There should be a first fix of ductwork while your studwork is being installed, this should be discussed with your architect & builder. This is much the same as plumbing or electrical work, except that the pipes are much large, so cannot be accommodated within walls or spaces easily unless planned for"

Hope there's no issues posting this

imitation

Prodigalson wrote: »

Full agreement,good luck with the build and HRV,you've researched yourself I'm sure but here's something I came across on another forum worth a read,will pm you the link it's a good discussion with some useful links here's an extract...you may have seen it all before.

"Flexible ducting not recommended, less efficient, more places for condensation and dirt to get trapped. So make sure rigid ducting is specified.

If you look up sap Appendix Q, you will see that they state that the efficiency of the units is only valid for rigid ducting. The Appendix Q rating is the efficiency rating used in BER certs so ensure the unit you getting installed is rated if you are concerned about having it's efficiency reflected in your cert.

All pipes should be insulated, especially in attic, where temperature difference can lead to condensation if they are not adequately insulated, also the heat would be lost to your attic space instead of finding it's way back to the heat exchanger in the MHVR.

Get quotes from a number of suppliers so you can compare.

There should be a first fix of ductwork while your studwork is being installed, this should be discussed with your architect & builder. This is much the same as plumbing or electrical work, except that the pipes are much large, so cannot be accommodated within walls or spaces easily unless planned for"

Hope there's no issues posting this

Thanks for that, flexible ducting is a common no no I have heard, but its always worth ferreting through this stuff. My builder has made all the right noises about HRV, including some points I didnt really consider (kitchen extract through HRV costing extra and a bit like it), so I`m happy to go with him on it.