Energy performance certificates

Alan_Brown

I was watching Channel 4s Building the Dream program, about self builders, and one thing amazed me. The presenter is an architect/designer and he talked a couple out of fitting a GSHP because they had access to mains gas. His logic was that it was cheaper to fit a gas boiler (it was, by about £10k) and as their home was super insulated and airtight, they wouldn't need to run the boiler much anyway.

They followed his advice, but later in the show said that it effected their EPC rating, narrowly bumping them from an A rate to a B rate. I (and the people on the TV) were astonished by this. They had enough insulation to need virtually no heating, and would just use their boiler for domestic hot water (something that heat pumps are notoriously inefficient at) and yet still couldn't manage an A rating.

As well as being super insulated and air tight, they had heat recovery ventilation and solar panels. Makes you think that if they can't get an A rating, then who can? is the EPC system fit for purpose?

Martyn1981

That's interesting. Is it anything to do with the CO2 impact of a property on its EPC?

Had they gone for a heat pump, would that have been more efficient in terms of CO2, hence the issue.

But, big but here, if it was so well insulated, had MVHR, and only needed a very small boiler, why GSHP, wouldn't an ASHP have been enough, much smaller bill, and hopefully use some of the PV excess too.

Potentially no gas, and no gas standing charge too?


Disclaimer, my house is A rated (actually good B rate, but low A rate if I had underfloor insulation and CWI, both of which I have, but couldn't be confirmed for the certificate). I don't think my house should be an A, when thought of in terms of insulation/heating, but apparently has something to do with all the PV, scoring bonus points. From your description of insulation, MVHR needed and PV, something doesn't sound right.

Mart.

Alan_Brown

Martyn1981 wrote: »

That's interesting. Is it anything to do with the CO2 impact of a property on its EPC?

Had they gone for a heat pump, would that have been more efficient in terms of CO2, hence the issue.

But, big but here, if it was so well insulated, had MVHR, and only needed a very small boiler, why GSHP, wouldn't an ASHP have been enough, much smaller bill, and hopefully use some of the PV excess too.

Potentially no gas, and no gas standing charge too?


Disclaimer, my house is A rated (actually good B rate, but low A rate if I had underfloor insulation and CWI, both of which I have, but couldn't be confirmed for the certificate). I don't think my house should be an A, when thought of in terms of insulation/heating, but apparently has something to do with all the PV, scoring bonus points. From your description of insulation, MVHR needed and PV, something doesn't sound right.

Mart.

I'm not sure whether an ASHP would result in a smaller bill than gas as they are quite inefficient when heating water past UFH levels (around 40C). The self-builder on the program had super insulation and pretty much didn't need heating, so his main requirement would have been for hot water. I think you can arrange a gas tariff that does away with standing charges, but has a higher unit price for gas (which wouldn't be an issue if you're a low consumer).

Are you a self-builder? It's an amazing achievement to hit an A rating (according to some figures I've seen, only 0.09% of UK properties are A rated and 8.39% B rated. I guess you have external wall insulation all around? The self-builder on the program had EWI thickness of 300mm Kingspan type insulation and triple glazing. Hence my amazement that he could only reach a B rating. I think the EPC rating is based primarily on floor space, and it was a large home (on TV), so perhaps that's what cost the self-builder in the end? Do you have a small footprint house?

I tried to google the requirements for A rating but couldn't find definitive requirements, other than a house receiving the full 100 points (A rating) had to run on virtually zero energy. Could I ask what insulation levels (roof, walls and floor slab), glazing and green tech you've invested to hit an A rating on your property?

Now I have solar, I'm really getting into the idea of reducing the carbon footprint of my home, so any info you can give me would be really interesting.

Alan_Brown

Sorry, I have just noticed you mentioned CWI and realised this was Cavity Wall Insulation. Is that the kingspan type insulation? What sort of thickness have you installed? How did you deal with the wall/roof junction to make sure the insulation made an unbroken envelope?

Owain_Moneysaver

Alan_Brown wrote: »

is the EPC system fit for purpose?

Of course not. But what do you expect when a typical EPC costs £50 and will be done by someone who doesn't have the assertiveness to sell double glazing?

Alan_Brown

I found this information on a solar site, providing advice to improve EPC levels to D to qualify for the upper solar FIT payments:

"There are a few relatively cheap and straightforward improvements to a domestic property that will contribute to achieving an EPC ‘D’ rating.

Condensing Boiler – 47 SAP Points
Cavity Insulation – 13 SAP Points
Roof Insulation – 10 SAP Points
Cylinder Stat and Insulation – 8 SAP Points
Double Glazing – 4 SAP Points
Low Energy/LED Lighting – 2 SAP Points

The majority of homes will already have a condensed boiler, meaning a simple and relatively cheap insulation of the roof or cavity wall will result in EPC ‘D’ status right away. For this reason, home insulation stands to be the single most effective method for domestic properties in becoming solar ready."

Alan_Brown

From another site:



This means my 4kw array gives me +20 SAP Points. I have an immersion heating diverter for the PV, but I don't know if this counts as Solar Thermal?

Martyn1981

Alan_Brown wrote: »

I'm not sure whether an ASHP would result in a smaller bill than gas as they are quite inefficient when heating water past UFH levels (around 40C). The self-builder on the program had super insulation and pretty much didn't need heating, so his main requirement would have been for hot water. I think you can arrange a gas tariff that does away with standing charges, but has a higher unit price for gas (which wouldn't be an issue if you're a low consumer).

Hi Alan. I was thinking about the cost of a boiler and minimal heating needs, versus an ASHP, perhaps with the water temp topped up by an immersion heater.

Not sure if that's better, but would work with the PV, if heating needs minimal, and removes the need for one service. If paying for a gas connection then the savings could be higher still.

Just pondering the economics, as I was surprised GSHP got a mention at all if heating needs are so low.

Alan_Brown wrote: »

Are you a self-builder? It's an amazing achievement to hit an A rating (according to some figures I've seen, only 0.09% of UK properties are A rated and 8.39% B rated.

Nope. have done some jobs, such as convert the loft, with supervision from a carpenter who built the stairs for me. But only a keen DIY'er.

My main point was actually self-critical, as I have a 1930's semi-detached. Yes I've done all the stuff we're told to do, CWI (50mm approx, small cavity), low energy lights, underfloor insulation where the floors are raised. 80mm of PIR under the kitchen floor when we dug it up. Combi boiler (but not condensing yet), DG all round, loft floor insulation, plus loft roof insulation.

But ....... it's still a 1930's semi, and I don't see how it can get an EPC of A (subject to disclaimer above).

Looking at your last post, I'm guessing it's down to the sizeable PV system.


I'm a big fan of insulation. Recently built a store-room side extension (garage without a garage door). As it's unheated I didn't have to install insulation for building regs, but hard to insulate later on if you change your mind, and the cost (during build is cheap), so 100mm PIR in the floor, 50mm in the walls, and 125mm in the ceiling. Also fitted DG exterior UPV doors at each end. The insulation probably added £500 to the build cost. Good investment I think.

You may be interested to know that the door from the house to the room had to be an exterior DG door, as the room is classed as external (semi-external) being unheated. So I couldn't cut a hole in the side of my house, unless I made sure it was replaced with a door that met building reg approval.

Mart.

Alan_Brown

There must be a formula involved because when I added up the SAP Points in my initial post for the condensing boiler, double glazing, cavity wall, etc, plus the 20 points for 4kw and above solar, it came in at 104 out of 100!

Lol, clearly there is more to the SAP calculations than just adding up the individual items. I agree with Owain though, the EPC calcs really don't seem fit for purpose.

matty2767

I would add +3 for the divertor but there will be an argument that you might not divert anything or at least divert less than you would in comparison to thermal.

Our EPC before panels was 77 so I am now at 100 too. (77+20+3) but we don't run zero energy

Alan_Brown wrote: »

From another site:



This means my 4kw array gives me +20 SAP Points. I have an immersion heating diverter for the PV, but I don't know if this counts as Solar Thermal?