Block build - is an A2 BER rating possible?

G

Goldie

Registered User
Messages
37
Hi,

Trying to spec our build at the moment. 2,500 sq ft storey and a half. The preferred build option at the moment is block built with the insulation spec (and required detailing around opes etc). as advised by Kingspan to achieve an A2 BER . The wall insualtion will be 80mm cavity and 42.5mm insulated plasterbaord on the internal side.

We will also be installing a MHRV system and the heating will (probably) be an air to water heat pump.

I also intend getting an air tightness test performed

Before i commit to this i am just a little concerned, it my spec correct? Am i missing something that will mean we will end up with excessive heating costs from the heat pump?

Just looking for a bit of reassurance really that the above will acheive our aims of a comfortable, good performing efficient home that has low ongoing running costs. Block build is the preferred option, don't want timber frame.

Anything else we should do? Anyone build with a similar spec, how is the house performing?

All advise and experience welcomed.

Thanks,

Goldie.
 
Hi using the spec you have outlined you should achieve the rating A, and at least100mm under the floor of the build, i have just build 4000 sq ft home with (hrs) and similar spec to yours, but went 50mm kingspan on external walls and 150mm under floors, it is important to remember to use the best quality materials for sealing the house ie membrane and tapes etc, the air test was 100%, good luck
 
The biggest factor effecting you getting to an A rated house is the effeciency or COP of yout Heat Pump unit. You wont achieve an A2 with an air to water heat pump unless the COP is well over 4.0 and it has to be an independently tested COP that will be accepted by SEI.

Kingspans references are a bit loose when it comes to the heating side of things.

Get a certified BER assessor to look at the project for you and he will tell you exactly what you need to achieve.
 
You could of course obtain an A2 rating and still have a shockingly expensive house to heat.

The BER process is a paperwork exercise i.e. it assumes good workmanship which is far from a guarantee. The only measurable element would be your airtightness but a blower door test is not compulsory.

In a nutshell, quality workmanship will be the key to success for you.
 
Hi,

Accept that one of the key elements is quality workmanship and detailing. I am a fussy person though and will be very strict on this!

SAS, i would be going for an airtightness test. Once a good result is achieved on the blower test and the A2 BER detailing does that mitigate risk of having an expensive house to heat?

Chimpster, can you please expand on your point, what is COP? Do you know of an air to water heat pump with a cop of over 4 that has been certified by SEI? If so, please pass on details.

Thanks.
 

1. with respect, do you know enough about technical detailing and workmanship to be fussy and strict?

2. the higher the levels of insulation and air tightness, the lesser the output required from your heating system. The prime example of this is passive houses which are so well insulated and air tight, that they need a tiny heating system... typically a 1-2 kwhr element... rather than a 30-35 kwhr oiler in a traditional build.

my issue with a block build is that the tradesmen building it would not be used to the level of detailing and workmanship required.......
prefabricated off site houses have a much lower tolerence level than 'open system' houses such as a block build.

if i was aiming for an A2 house, i would first find out by, by a prelim BER assessment, what level of air tightness i need to reach this rating.,.... and then get the contractor (assuming you are using one) to sign a contract guaranteeing this level of air tightness.

if you are going with a direct labour build, forget your A2.. as sas says above it would only be a paper exercise and would not reflect the true outcome of the build...
 
Would it be worth trying to contractually specify the air tightness that you wish to achieve and that thermal imaging will be used to identify any shortcomings in the insulation.

I'm currently trying to do the best re insulating and air tightening my renovation project and just last night spent a few hours going over and resealing some of the tapes around the new windows that were not up to "my" standard. My builder and his crew are doing their best but still I've had to carry out some improvements myself along the way. I'm slowly starting to except that working on your own home is a labour of love, however to your hired builder it just another job that they want to finish asap. So unless you've got an exceptional caring builder lined up (or maybe that they are family) then I feel that it's inevitable that work carried out that is hidden from view may possibly not be up to your standard. This can be due to many reasons such as workmanship, misunderstandings etc.
The reason I mention this and to address your initial post is that another possible way that I think might guard you against substandard work (as well as watching everything yourself) is to specify that a door blower test will be carried out and that it must achieve a certain level of air tightness (inserting your desired figure). Also re insulation that thermal images will be taken of the build in order to identify any shortcomings in that area.

Fran
ps I'm very happy with my builder/renovator (just in case he's reading this)
and apologies if this is pulling your post in a different direction.
 

COP is the effeciency of the heat pump unit. Typically a good quality ground source heat pump when independently tested will achieve a average COP of 400% (or 4.0) or more.

However AFAIK an air source heat pump will not achieve an average COP of this standard. In the peak of winter where the air tempretures are low outside the COP will drop and instead of your heat pump heating the water an electrical element within you tank may kick in and do the job which basically means you could be charged upto 19 c per kWh for your heating.

Maybe somebody has some independent test data for air source heat pumps?
 
Syd / Fran - that is a good idea in relation to the specified airtightness test result. Advice like that is the reason why i posted on here!

Syd - with respect i never said i would be reviewing the work, thats why i am paying professional advisors! I am fussy, meaning, i will be stipulating to them what i want to achive - in my view it will be their job to ensure the build achieves this. If not, they need to be clear with me from the outset that they cannot do this.

In relation to the COP / air source heat pump efficinecy point mentioned by Chimpster could anyone expand or point me to some independent test data?

Lastly, with regard to a stove, how do we achive an enclosed airtight system? Can it be vented from underneath (a pipe in the ground) or is a chimney required? I read previous posts but am a little confused as to what it the best solution.

Thanks everybody for your help.
 

goldie... thats the perfect attitude to have. Hopefully you can keep it up during the build...

the hardest thing you will do is finding the right professionals to hire.. both building and designing....
 
Goldie said:
Lastly, with regard to a stove, how do we achive an enclosed airtight system? Can it be vented from underneath (a pipe in the ground) or is a chimney required? I read previous posts but am a little confused as to what it the best solution.
Click to expand...

The basic way that room sealed stoves work (solid fuel) is that they use a standard flue\chimney to vent smoke etc. and they have an additional opening on their base or at the rear to which you attach an external air supply. Typically this a 100mm pipe that draws air from outside.

Talk to www.murphyheating.com (These are pretty well up. I have no connection and have never bought from them).

If you are interested in more info. on these then just pm me. I've looked into it a fair bit but haven't bought yet.
 
Franm said:
Would it be worth trying to contractually specify the air tightness that you wish to achieve and that thermal imaging will be used to identify any shortcomings in the insulation.
Click to expand...

Thats an excellent point Franm. I should point out that we offer these type services in the sector.

We are seeing an increasing amount of people tying in their contractor to getting either a specific rating or a specific air tightness result. The contractor really doesn't mind working to a target because at the end of the day he is going to charge the customer for the advice he gets on meeting these targets and the extra products & services needed to meet these targets. Its an excellent idea but not all self builders are that well informed about these issues.

There is no reason why a properly built block house cant achieve an air tightness of below 3 m3/hr/m2. The key is getting a provisional test done at first fix stage before the house is plastered on the inside.
 
You must log in or register to reply here.
Menu
Log in
Register