BER lingo

HoofRocks

Hi there

we got our ber cert today and there are a couple of figures on it that I am unsure about.Ive read about them here on boards but im not 100% on what they mean

Energy value kwh/m2/yr is 43.37

another one is result of air permeability test in ac/h 0.100 - I think this is airchanges but is 1 not a very low result?

now I know I can go back and ask the accessor and im not looking for free professional advice but can anyone briefky elaborate on what this means for us..

Thanks in advance

sydthebeat

The energy value is what it says, it's the assessed kwhr energy demand, per meter squared, per year.
Multiply it by the floor area to get an (approximate) energy demand for the whole dwelling per year.

The air change rate is gotten by dividing the air permeability result by 20. So an air change rate of 0.1 is an air permability of 2.

Is this a provisional assessment before building, or a final one.

HoofRocks

sydthebeat wrote: »

The energy value is what it says, it's the assessed kwhr energy demand, per meter squared, per year.
Multiply it by the floor area to get an (approximate) energy demand for the whole dwelling per year.

The air change rate is gotten by dividing the air permeability result by 20. So an air change rate of 0.1 is an air permability of 2.

Is this a provisional assessment before building, or a final one.

thanks for that. It is a provisional one. So is that 2 air changes per hour?

sydthebeat

HoofRocks wrote: »

thanks for that. It is a provisional one. So is that 2 air changes per hour?

No.

The "blower door" test will give you a result of the 'air permeability' of the dwelling. This is a measure of how air tight your building envelope is. This really is then divided by 20 to give you your 'air change' rate.

So your air permeability result of 2 is divided by 20 to give you your air change rate of 0.1 air changes per hour.

HoofRocks

sydthebeat wrote: »

No.

The "blower door" test will give you a result of the 'air permeability' of the dwelling. This is a measure of how air tight your building envelope is. This really is then divided by 20 to give you your 'air change' rate.

So your air permeability result of 2 is divided by 20 to give you your air change rate of 0.1 air changes per hour.

Thanks for that sydthebeat. Is 0.1 an average rating? Is it acheivable

4Sticks

HoofRocks wrote: »

Thanks for that sydthebeat. Is 0.1 an average rating? Is it acheivable

That is approaching passive house. Not average not easy.

sydthebeat

HoofRocks wrote: »

Thanks for that sydthebeat. Is 0.1 an average rating? Is it acheivable

Minimum levels under 2008 regs was 10, reduced to 7 under 2011 regs.

2 is challenging and will need an appropriate strategy to achieve.
Bog standards will not suffice.

HoofRocks

sydthebeat wrote: »

Minimum levels under 2008 regs was 10, reduced to 7 under 2011 regs.

2 is challenging and will need an appropriate strategy to achieve.
Bog standards will not suffice.

If 7 is acceptable why would we need 2? I'm worried we won't acheive this and then what happens?

sydthebeat

HoofRocks wrote: »

If 7 is acceptable why would we need 2? I'm worried we won't acheive this and then what happens?

Is "minimum" acceptable?

It's a measure of how fast your dwelling losses heat through draughts. The higher the number the worse the result.

Is there a heat recovery system purposed?

HoofRocks

sydthebeat wrote: »

Is "minimum" acceptable?

It's a measure of how fast your dwelling losses heat through draughts. The higher the number the worse the result.

Is there a heat recovery system purposed?

Yes definitly a mhrv. High level if insulation air to water heat pump with underfloor. Who is the best person to advise on air tightness engineer? Or specialist company

BryanF

HoofRocks wrote: »

Yes definitly a mhrv. High level if insulation air to water heat pump with underfloor. Who is the best person to advise on air tightness engineer? Or specialist company

Your designer provides construction details & specification and the builder or specialist sub-contractor does the work. Remember 2 ACH means the volume of air in you building leaks out if your building twice an hour. You can do better especially if your installing MVHR.

sydthebeat

HoofRocks wrote: »

Yes definitly a mhrv. High level if insulation air to water heat pump with underfloor. Who is the best person to advise on air tightness engineer? Or specialist company

Well in my opinion when a hrv is being installed 3 should be the highest acceptable result. So 2 is in that range and a good figure to aim to.

HoofRocks

sydthebeat wrote: »

Well in my opinion when a hrv is being installed 3 should be the highest acceptable result. So 2 is in that range and a good figure to aim to.

That's a bit more re assuring thank you folks

4Sticks

BryanF wrote: »

Your designer provides construction details & specification ...

or not.

BryanF

4Sticks wrote: »

or not.

But that's what we're here for 4sticks, pearls of wisdom

HoofRocks

Not would be our case
Designer didn't provide this so hopefully engineer can shed some light on it

BryanF

HoofRocks wrote: »

Not would be our case
Designer didn't provide this so hopefully engineer can shed some light on it

Good luck with that, as this is generally and architectural item and not an eng item. I'd suggest your arch at least writes in a Preformance standard for air-tightness into your contract with the builder.