HRV having a negative effect on BER

Curious Geroge

Our BER accessor tells me that our planned HRV will mean we won't meet the ccurrent regs but not installing it and going with trickle vents gives us our A3 rating. Anyone else experience this ?

Old Jim

Mine was similar but it was the de-rating of the heat pump efficiency when it was producing domestic hot water that was the real cause of it. The ber reduced the efficiency of the heat pump by about half. The net effect was that I would have to install solar panels or remove hrv and install wall vents like you.
I haven't really found any solution to the problem yet. One supplier has told me that an update of the DEAP software due in mar would correct the anomaly.

sydthebeat

edit: duplicate

sydthebeat

firstly make sure the assessor is not using default MHRV values (ask him what product he is applying)

secondly make sure that a decent air change rate is applied ie 0.15, which is an air infiltration rate of 3

come back to use when this is done and let us know what difference this makes.

as for your issue Old Jim, thats a known anomaly in DEAP. Its basically telling you that the lower your energy demand, the less your heat pump can provide. Until they change the algorithms that's what we are stuck with.

Its not the BER that cuts its efficiency by half,, its a proven fact that HPs are a lot less efficient when they need to boost up to provide hot water, youre basically heating water by electricity at that stage.

MOTM

sydthebeat wrote: »

thats a known anomaly in DEAP. Its basically telling you that the lower your energy demand, the less your heat pump can provide.

...so, if there is less heat demand, the heat source has to provide less heat to meet that demand.
What's anomalous about that?

sydthebeat

MOTM wrote: »

...so, if there is less heat demand, the heat source has to provide less heat to meet that demand.
What's anomalous about that?

because you are left with the perversion where you have the ability to meet regulations by make the build LESS efficient.

The regulations should be based in a percentage of final energy demand rather than a nominal "per sq m" figure which we have currently.
This is a well accepted perversion in the regulations and thus the software.

The anomoly is that in the case above, if the Heat Pump is capable of providing the renewable energy requirement at say 'X' energy demand... then it is obviously more than capable of providing the renewable energy requirement if the demand becomes 'X - 10%' ie more efficient dwelling.
The regulation does not represent this.

MOTM

...so its an anomaly in TGD L which tells DEAP what to do for compliance checking.

sydthebeat

MOTM wrote: »

...so its an anomaly in TGD L which tells DEAP what to do for compliance checking.

yes thats one way of looking at it... but the anolomy still exists within the procedure.

Compliance with DEAP is what informs Part L compliance.

The algorithms in DEAP have been written to reflect the prima facia compliance of 10kwh/m2/yr renewable heat energy requirement.

So the requirement is a blunt instrument... but the anolomy still exists within the parameters of the software, thats how it is programmed.

MOTM

...if the anomoly wasn't in DEAP, then I guess it wouldn't be following TGD L

sydthebeat

MOTM wrote: »

...if the anomoly wasn't in DEAP, then I guess it wouldn't be following TGD L

exactly

Curious Geroge

Response from SEAI
"SEAI is not in a position to change the requirements set out it TGD L."

So, it seems the only way to be complaint with using a heat pump is not to use HRV (thereby no airtightness) and have natural ventilation..

At the moment it looks like we have to go with gas and solar to have airtightness and a HRV.

Any other opinions out there ?

sydthebeat

Curious Geroge wrote: »

Response from SEAI
"SEAI is not in a position to change the requirements set out it TGD L."

So, it seems the only way to be complaint with using a heat pump is not to use HRV (thereby no airtightness) and have natural ventilation..

At the moment it looks like we have to go with gas and solar to have airtightness and a HRV.

Any other opinions out there ?

you would be better off putting that question to your local building control officer.

the actual regulations actually states that "a reasonable portion" of energy should come from a renewable source. The TGD L provides a prima facia method to comply.

I have read in passive house+ magazine where a BCO has said he would accept an argument where DEAP doesnt convey compliance.

BryanF

sydthebeat wrote: »

you would be better off putting that question to your local building control officer.

the actual regulations actually states that "a reasonable portion" of energy should come from a renewable source. The TGD L provides a prima facia method to comply.

I have read in passive house+ magazine where a BCO has said he would accept an argument where DEAP doesnt convey compliance.

+1
my local BCO have accepted the 'reasonable percentage' argument.