IGP

I'm not so sure on electricity being a one-way bet, unless all you're thinking about its price cap/fixed tariffs. Taking Octopus agile as the most extreme example of the smart tariffs, it's clear that the average price is in the 15-18 p/kWh range if you can avoid lots of consumption between 4-7pm. Given that a HP would run low and slow all day, the vast majority would be at these averages (you could also do a setback during the 4-7pm peak). There are numerous other smart tariffs, each with their own pros and cons but they usually mean there are bargains to be had if you want to take them.

Which is why I’ve come to the conclusion that we probably should be only recommending 300mm loft insulation, CWI (if have cavities wide enough) and upgrading to DG from SG for *most* properties, unless you happen to be doing more work anyway and can insulate more while there. New builds should be much higher standards. These are the highest impact per £ invested. And then HPs at <45c design flow temp as that is around at the point where SCOP for most HPs beats the spark gap and saves money for people (and be therefore can be seen as better, not just equal to gas). But that’s just my rules of thumb.

I have the same, I installed between the MVHR unit and the supply and extract distribution boxes. You want to attenuate the fan noise of the unit to the house, not the the outside to the unit - unless i'm massively mistaken! Hope that helps

I'm not so sure it's going to cost a ton in energy and can in fact be less. This is the Valliant Arotherm Plus table, which is probably there or there abouts a good approximation for most heat pumps. If say, I've got a property thats got a annual usage of say 10,000kWh of heating requirements which roughly approximates to a heat loss of 4kW at design outdoor temp (10,000 / 2500 degree days) and I run it at a 'bog standard' 55c flow , it gives a SCOP of 3.06, which would use approx 3268kWh/year elec. If I insulated the same property, and knocked of 1kW of heat loss of design temp (so now it's 3kW, 25% reduction of overall heat loss) by using IWI - that would be approx 7500kWh annually heat demand, and at the 55c flow temp would mean an annual use of approx 2,450 kWh / year. However, if i did nothing to the fabric, but instead upgraded the heating system to run at 35c flow at the outdoor design temp, that would give me a SCOP of 4.48, which would mean an annual electricity use of (10000/4.48) = 2,232 kWh / year.

Maybe I’m just a renegade, but when it comes to IWI - I’m usually of the opinion of don’t bother. Just make the sure the emitters are sized for 40c or less (ideally 35c) flow temperature on an ASHP and get the benefits there rather than potentially causing interstitial condensation issues with IWI. Much less risk and still high comfort with low energy inputs.

What @JohnMo says. Just slapping a HP in and guessing at the setup with doing proper heat loss calculations, system design and using on/off controllers is asking for trouble. What is your brother’s aim with the swap to the heat pump (apart from doing the right thing environmentally)? Is it low running costs, or low installation costs?

From what I understand, the manufacturers actually don't when they are pushed by people who know what they're talking about. They include buffers / LLH's in the manufacturers instructions, but it's just excess stuff to prevent callbacks.

There is also the Viessmann Vitocal 150 /151 A's, they also can integrate with the OVO tariffs (I assume any others that might work in the same way in future) and seem to be considered by some of the heatgeek engineers on twitter as the dogs danglies. I'm leaning that way when i move from my gas boiler to ASHP.

I think Glyn Hudson found this exact thing, he starts talking about it around 8mins in the video

Just remember you if you put any membrane down, it’s a breather membrane for the cold side and a vapour check membrane for the warm side, as well as don’t forget to tape it also. The breather membrane on the outside does the hard work of preventing wind wash, whereas the vapour check on the warm side prevents warm humid air crossing into the insulation and condensing. Ideally you need both. Or use foil backed PIR and foam and tape the area you install it. The foil prevents vapour moment, so getting a snug as fit as possible is key.

I’ll just leave this here re hydrogen. V interesting.

Depends. They have to be part of a strategy, and a very clear one at that. If it’s acknowledging that the skills base for low temperature heating isn’t there and there’s a very clear signal to industry to get their finger out and train and implement low temperature heating design by X date (say 2030 for argument) whilst also decarbonising at the same time and no new gas appliances after 2040. That could fly. If there’s no explicit strategy, then we have to go through the hard yards upfront in changing the culture to low temperature heating design, but it won’t be pretty. But if we throw hybrids in here, that just makes it worse as it’s extends this messy period where the training and culture of heating design isn’t moving on, possibly an even worse place to be.

It looks like he’s gone for what he’s losing in actual heat loss, making up (and possibly more) with efficiency of the system.

The system is visible on https://heatpumpmonitor.org/system/view?id=139 so make of it what you will but it looks impressive to me.

If you’re going down the rabbit hole of research, this is where I found the most easy to digest information by just going through the back catalogue of the videos in these channels. Completely eye opening. https://youtube.com/@heatgeek?feature=shared https://youtube.com/@urbanplumbers?feature=shared

I'm actually sort of jealous of your blank canvas! If you can get someone to do your floor - think about underfloor heating - this is an enabler for the highest efficiencies in a heating system as its basically the biggest radiator you can have. On heat pumps, if your knowledge comes from reading anything in any newspaper or from the comments at the bottom of articles on heat pumps - forget what you think you know. They don't need highly insulated and leak-free houses, they could heat a barn if designed to do so. Insulation helps make the heat pump you buy smaller and the emitters you need to be smaller, i.e. if i put loft insulation in my home it's heat loss goes from 6.3kW to 3.8kW (obviously already done it) - and it means i can by the 4/5kW heat pump size rather than a 7/8kW. (side note that efficiency can actually be marginally higher on higher heat loss properties, but that isn't a reason not put insulation in, see the graphic below where the 10kW model at 35c is 5.03 vs the 4.48 on the 5kW, but the 5kW is much cheaper to buy) Whilst you could do it with oil and have big radiators and low flow temps - the efficiency gains on oil / gas are in the region of going from 75% to 85% efficiency - so like 10% increase, not nothing. With heat pumps you can be talking multiples. In the example below on a Valliant heat pump, going from 55c flow to 35c there is a increase of 142% on the 5kW model. On your point about being held to ransom by electricity companies - i would argue its almost exactly the same with heating oil companies or whatever. Potentially think about a woodburner as a backup if you're nervous? All I would say is that you need a good engineer - not just any joe bloggs off the street to do a heat pump job - whilst they are actually technically simpler than oil / gas systems - the training across the industry is patchy at best. To find good engineers - look at some of the ones on HeatpumpMonitor.org that are clearly doing great installs. Last thing i'd ask is a simple question - do you think oil heating is the future?

Oh and empty your cavities and fill with EPS beads as described earlier for nice full and even insulated walls. 😃

I recently (over the last year) renovated my house - 1920's semi with 65mm cavity, I had grand plans of insulation everywhere - doing EWI & IWI. Any way, long story short I worked out that loads of insulation is overrated in our climate - law of diminishing returns. 300mm of loft insulation, cavity wall insulation if you can and if you've got suspended timber floors and happen to be doing work there do so. Beyond that, I'd go so far - controversially as saying don't bother. Exceptions would be thermal bridges that would cause condensation. Sort the ventilation strategy. Ultimately insulation doesn't *make* you warmer - it means the space loses heat slower, you still have to heat the space (caveats apply to that broad statement around thermal bridging / uneven insulation across elements) The focus then should be heat pump system designed to the lowest flow temperature you can (<40c) and is weather compensated. This is where you would get the comfort and lower energy bills. Save your money for a well designed heating system.

Can I ask a stupid question - what is your ultimate aim?

HPs are great and can easily be cheaper and more comfortable than gas central heating, but they are different beasts vs gas boilers. They can be a bit of a learning curve as you don’t run them the same way. I would get someone like a heat geek as mentioned earlier to come round, and explain and setup the system in an optimal way for you. It’s just not worth the stress IMHO.

Might be worth taking a look at to see how they did underfloor heating as well. About 5 mins in.

Need, no. But you could for that extra bit of performance.

I would echo the A2A (air con) sentiment. It’s not resistive so doesn’t run glowing hot and will be 2-4 times more efficient than resistive heating. If you’re there for a while, worth it.

This is the kicker, I personally would scrap the BUS but offer 20 year interest free loans to spread the capital cost.

As others have said, something doesn’t sound right to have those kind of bills and still be a bit cold unless you genuinely have an uninsulated mansion.