ASHP retrofit suitability - 1960s chalet bungalow

[Ommm]

We moved into our current house in the spring.  It's a 1960s semi-detached 4 room bungalow in Cambridgeshire, brick construction and a tile roof.  Sometime in 1970s the loft was converted to add two rooms in the roof.  The property has an oil boiler, electric shower and a woodburning stove in the living room.  Cooker is electric. EPC was done in 2011 and is E54 – and says the area is 99m2. 

 

There's cavity wall insulation and ~20 year old uPVC double glazing. The conversion has vertical stud walls and dormer windows facing east.  I've been fitting window film to the dormer windows (the solar gain in the summer is massive).  The loft floor has 100mm fibreglass insulation and 100mm fibreglass batts are behind the stud walls in the conversion.  I'm guessing the ground floor is uninsulated beyond the wood flooring and carpet underlay (there's an air brick going under the floor but I don't know the floor construction). The site appears to be relatively windy, although that's hard to compare. It's unclear if the conversion flat roof is insulated - thermal camera pictures suggest it might not be.

 

It's been on the todo list to look at replacing the boiler, and it has now been declared unserviceable (although still working inefficiently for now).  We haven't been in for a winter so we don't know what the oil consumption is like.  The boiler is a 11.7-14.7kW model which appears to have been fitted with a jet hotter than 14.7kW (hence its impending demise).  The radiators are mostly single-walled on conventional copper pipes (~20mm diameter). 

 

In our previous place (a sprawling 3-bedroom bungalow, worse insulated but with solar thermal) we used 1200 litres of oil over the year, which is 12400kWh. We only ran the heating sporadically on '1 hour' mode for maybe 4-5 hours a day though. 

 

I've been looking at ASHP but I'm a bit uncertain as to how it would work in a retrofit like ours. The RHI and GHG and our current boiler demise make this a bit more pressing than it might have been.

 

I'm assuming that an ASHP installation would also involve improving the loft insulation and plugging any air gaps (eg under the conversion floor).  We wouldn't be able to install UFH so that would leave us with radiator upgrades I presume?  We'd replace the hot water tank with a thermal store and fit a tank-fed shower.  We might also look at solar thermal or solar PV (lean towards thermal because roof space is limited and it works out a bit better with RHI and GHG).  We're also concerned about noise - we're going to view some ASHP installations next week to hear for ourselves.

 

Some questions: 

 

1. Is this kind of property suitable for an ASHP, or is the insulation just not good enough?  I've heard all the horror stories about undersized ASHPs in insufficiently insulated houses, but I don't know what's 'good enough'.  

2. My wife likes to have the place cool, and likes opening windows for the fresh air.  If we set the temperature to say 18C, would the system cope with the occasional window open or would that kill the efficiency?  It would only be in one room at a time (except during the summer when we wouldn't run the ASHP).  I don't think the house would be suitable for MVHR.  We also have cats so closing doors is more difficult.

3. Given the 'upstairs', how do we prevent all the heat escaping into the upper rooms and downstairs being freezing? With a boiler there's a constant large heat flux into the room – I'm not sure you'd get that with low temperature rads.  Obviously TRVs would reduce the output upstairs, but I'm concerned about hot air escaping upwards. 

4. Can radiator upgrades be done by replacing single-wall with double/triple wall, ie keeping the same radiator wall area?  Some can be enlarged but those below windows cannot.  Others are in awkward corners, eg kitchen with limited wall space.

5. The woodburner is drawing in room air.  Would that drive a coach and horses through our efficiency?  Obviously when running it is going to emit heat, but when not running there may be some leakage (eg you leave the fire to die down overnight but it still needs air, and nobody will be there to close off the vent when it goes out).  Is there any way to reduce chimney leakage (automatically?) 

6. Would it be too taxing to run the heating at a constant cold temperature say 17C and occasionally 'boost' up to say 20C?  We might boost using the woodburner, but other times we might want the ASHP to do the boost. 

7. I have quite a bit of computing gear that emits heat (eg 400W server).  This can cause overheating in the summer when there is solar gain from windows.  I'm concerned that further loft insulation is likely to make this worse.  Is there anything I could do to mitigate uneven heat input into the house?  It would be neat if I could extract heat from these appliances into the thermal store somehow.

8. In the summer cooling would be very much appreciated.  Assuming we fit an ASHP that supports cooling, any pitfalls?  I assume I'd need to install fan coils off a separate port of the ASHP, rather than the heating loop?  How does this compare with using a simple split-unit air conditioner? 

9. Would it make sense to fit fan coils instead of rads, so they could do both heating and cooling?  How would they compare size-wise?  (My wife is also sensitive to noise so we might be looking at fan-off mode for heating, with the fan for cooling only). 

 

I'm also wondering about other options.  We're off the gas grid. GSHP is going to be expensive (only 150m2 of garden).  Biomass seems like a lot of hassle, and space is constrained for a boiler house.  A neighbour has LPG which means the front garden is dominated by an ugly LPG tank. I would quite like to recover the space used by the oil tank so moving away from oil would be handy.  Wonder whether some air-to-air split units might be easier than an A2W system (although they would probably fail the noise test).  Or maybe a combination of smaller ASHP plus split units? 

 

I don't really want to get another oil boiler, but wondering how risky ASHP is...

[Onoff]

A number of my neighbours have buried LPG tanks. Two at least are now landscaped over. One changed from an above ground oil tank. Local scrotes lent over his fence and cut a bucket sized hole in the tank and fished it all out over the course of a dark night. 

 

Another has a semi buried oil tank in that it's a big hole with walk space around. The top of the tank is level with the surrounding ground that slopes up to the house. Fenced on 3 sides, the 4th side is adjacent to the road for easy tanker access.

Edited September 11, 2020 by Onoff

[Ferdinand]

Lots of excellent questions, but there's a bit of "Eric Morecambe" - all the right questions, but not *necessarily* in the right order.

 

The mantra you need is "Fabric First" - ie you can't size your ASHP etc until you have sorted out the quality of the fabric, as you have no way of knowing what you will actually need. So start with insulation (roof, wall, underfloor), air tightness, and arguably 2G windows. Many of your questions will have very different answers once this is done.

 

In any case, the funding for an ASHP will require you to insulate roofs and walls first as recommended by your EPC (they will make you get one) as part of the process.

 

One you have sorted out the Fabric your EPC will be more like 75 or 80, you will have cut your energy demand by about 1/3 to 1/2 and you will need an ASHP substantially smaller than the one that calculations will suggest now. That will be thousands less expensive. The type of Rads choose, or ufh, will depend on your fabric quality.

 

Also, there is currently a big funding package around which expires I think at EOY 2020-21 which may help with a lot of this, whilst funding for ASHPs etc will stay - it is a long term required trend for dealing with C02 emissions.

 

So imo the way to go:

 

a Get an EPC. Yours is horribly out of date and it may be useful to have a new one. The way RHI funding works means a further one may be justified after doing roof and wall insulation, and before the rest.

b Address insulation. Talk to the Energy Saving Trust and see if you can get loft and cavity wall insulation free; there may be a body in your area. If you can, do it. 

https://energysavingtrust.org.uk/  Find out if any free assessment is available. Not a half hour EPC, a real assessment.

c Wrinkle. Loft insulation may be dependent on less than 100mm being there already. If so, take it out before the survey, and you can use it eg underfloor later.

c Look into the current govt programme. See what help you can get. Not sure if  this is launched yet. Ask EST. You may want to consider other types of wall insulation.

d Do do underfloor insulation if you can - worth it in a suspended floor, which is what you probably have. That is one to do early before you get carpets, decoration etc.

e Wrinkle. The heating oil price is currently about 28p per litre. Autumn 2019 it was about 50p. Consider getting any oil you may need now.

f Attention to detail is really important. Keep asking questions. To get attention to detail you have to take responsibility and MAKE them do it.

g There will be lots of other stuff to think about, including ventilation.

 

You could do all of this quickly. Your call as to how you do it.

 

On your Qs in their order:

 

1 - Yes, after improving the quality of the fabric.

2 - Probably OK. Depends on the different house you will have created.

3 - TRVs are a basic to have. Will be different once you have restored. Think then.

4 - Yes. But you may prefer ufh. If the system is a few years old it would make sense to replace all of it - leaving pipework will save relatively little.

5 - Probably OK. Depends on the different house you will have created. Keep as a boost for now imo.

6 - Depends on the different house you will have created.

7 - Probably OK. Depends on the different house you will have created.

8 - Depends on the different house you will have created.

9 - Depends on the different house you will have created.

 

In my view things like GSHP are niche things for special situations and WBS for a nice to have unless you get free wood. ASHP should do it you upgrade the house, but will need to be designed at the time.

 

Is there a temporary fix you can do on your oil boiler to make it last a bit longer?

 

For some reason I get a feeling that you have qs 10 to 678 on a list somewhere. 

 

Cheers

 

Ferdinand

---------------------------

 

 

Edited September 11, 2020 by Ferdinand

[Ommm]

Thanks, lots of food for thought.  My questions were made up as I thought of them so definitely a bit stream-of-consciousness ?

 

A few clarifications...

 

I've been looking at the RHI and the Green Homes Grant.  We're eligible (I think) for 10K of GHG, which must be spent before end March 2021.  Needless to say, all the installers are going to be very busy over the next 6 months (the GHG is a bit of a poorly thought out scheme where there's no time to train up any more staff).  The GHG is paid upfront but deducted from the RHI payments, meaning you get the same money as the RHI but don't have to wait for it.  That means there's a perverse incentive to spend more on eligible items, since it'll mean once you've expended your GHG you get the remainder as RHI (but you have to wait for that part).  The RHI has been extended to March 2022, so slightly less pressure on that front.

 

The boiler looks like it'll run inefficiently but is still operating - unless something else happens.  The tank is almost full (got some at 19p/litre and used little over the summer). The main urgency is the GHG deadline and contractors' busy order books.

 

I agree with fabric first approach. although there's a limit in a place you're living in.  Loft access is horrible (no parts of the lofts are more than a metre tall, really awkward hatches), so I'm pondering about doing that insulation myself to avoid builders traipsing around the place.   It would need to be carefully designed due to the construction - plain old fibreglass would be problematic (due to height restrictions).  I've been in touch with a local company but they look like basic fibreglass-stuffers, as it seems is the insulation under the Energy Company Obligation (who want to tick boxes as fast as possible).  The windows aren't anything to write home about but I'm not sure replacement would be covered under the schemes, nor make a huge difference (eg double to triple - since the existing panels look in good order).  Low-E film may help a bit.

 

Floor insulation and UFH would have been something we could have done before moving in, but we already had our hands full with redecorating, and there was a pandemic on so even basic supplies were difficult to get. We didn't forsee the boiler replacement being that imminent and we can't really tear up the floors at this point.  I'd really like to do the flat roof but there are few approved contractors who will cover flat roofs, and the need for scaffolding means I reckon a non-approved contractor will be about 3K... and it doesn't leak at this point so doesn't seem urgent (I'd actually like to use the opportunity of having scaffolding up to add PV too - but that would be too much right now).

 

Good idea about getting a new EPC.  Is there a way to find someone who isn't just doing the estate-agent tickbox thing, but will do a proper assessment? (I have a Flir thermal camera and have been taking pictures of things - gives me some ideas, although we haven't had cold enough days yet).  Some of the ASHP vendors say the next step is an assessment for about £300, which they'll deduct if we choose to go ahead with them - but that would mean picking a supplier which we're not quite ready for yet.  I suppose that's roughly what you might pay for a decent EPC.

 

Maybe a plan might be to get the assessment and see what difference loft insulation is going to make, before going ahead and doing it.  Then we can assess what impact it would have on the ASHP sizing.  We probably want to do the insulation anyway for cost reasons, but would be good to find out what to do first.

 

Edited September 11, 2020 by Ommm

[Ferdinand]

OK. Glad to see that your head is screwed on and logical.

 

I think the GHG is well thought out for its purpose - the other half of the agenda was to help boost the economy back out of the Corona Slump quickly, for which it has done its bit by the short timescales. They will need to do something like this continually to address the older housing stock to meet the 2050 target. Since an average older house has about 2 - 3x the emissions of a newbuild, and 65-75% of the stock are pre-energy-efficiency emphasis, that is where the 80% of the emissions problem is on the pareto chart. I expect an announcement in the Autumn Statement about longer term stuff. Ditto RHI. 

 

So you think there is only one pot per property for RHI *and* GHG? Interesting. Had not thought about that.

 

Yes - insulation is under leftover ECO funding afaik. I have had about 3-4 of them over the last few years, and a new boiler or two where Tenants have been drawing the appropriate benefits. 

 

To emphasise:

 

* Do talk to the Energy Saving Trust to see if they know anyone will do an assessment cheaper. I would not want an assessment from someone trying to sell me something. Perhaps "Green Deal Assessments" are still available if you pay? £300 sounds steep - they used to be more like £100. 

 

Try asking an EPC assessor if he could do a fuller report - mine would as they are also Energy Consultants.

 

* Do think about cavity wall insulation. I know one friend who has had this free in the last 2 years.

 

* Don't forget underfloor insulation because 1 Without it underfloor heating will never be efficient (40%+ of heat would be lost downwards) and 2 You only get one chance which is now, as once the carpets are down you lose enthusiasm to dismantle it all again. The easiest form I know is lift every third floorboard and install rockwool with a staple gun, though that is a bit weak for ufh - the last one I did also had celotex sheets over the previous floor. Other ways get you more insulation-power.

 

* Don't necessarily go 3G mad - the good 2G is not actually far behind. Is it actually that much more than the film in £££?

 

* The RHI assessment will want a normal EPC, not a flash one.

 

ATB

 

Ferdinand

Edited September 12, 2020 by Ferdinand

[ASHP newbie]

On 12/09/2020 at 00:55, Ferdinand said:

So you think there is only one pot per property for RHI *and* GHG? Interesting. Had not thought about that.

I can confirm that if you get  GHG then it's taken off any RHI you may get later on  ie the govt claws it back. Only a grant if you don't qualify for RHI .

[joth]

54 minutes ago, ASHP newbie said:

I can confirm that if you get  GHG then it's taken off any RHI you may get later on  ie the govt claws it back. Only a grant if you don't qualify for RHI .

Thanks!
 

Could you point to where you found this? Just so I can continue my reading up to decide if I push  for GHG or just go with RHI.

GHG gets around the "must be metered for use (and metered for payment? who knows) if combined with cooling function" of RHI so simpler on that front. But GHG  will require me to get a third "formal" quote, even though I already have a  good price from someone that's being very helpful too.

 

[joth]

On 25/09/2020 at 14:34, joth said:

Thanks!
 

Could you point to where you found this? Just so I can continue my reading up to decide if I push  for GHG or just go with RHI.

GHG gets around the "must be metered for use (and metered for payment? who knows) if combined with cooling function" of RHI so simpler on that front. But GHG  will require me to get a third "formal" quote, even though I already have a  good price from someone that's being very helpful too.

 

 

Well, I just submitted my GHG application for the ASHP, let's see where that goes! If it's turned down I'll have RHI as a fallback

Honestly I'm carrying out more the 80% of the eligable primary and secondary measures so it's rather frustrating that the RHI eligible ASHP is the only one that is eligible for GHG too (installer needs a trust mark license; needs to be quoted independent of the rest of the project). Fairly par for course on these schemes