IGP

I'm coming to make peace with hybrids in theory, assuming they are more like the Intergas ones, where they are running for 100% of the heating time, just topped up with heat from the combi rather than stopped and purely running on the combi. Then it's such a marginal step (psychologically) to full ASHP the next time people upgrade their heating / hot water in say 2035 / 2040... I would tier the BUS payment to be say £4/5k rather than the £7.5k for full ASHP installs.

To be fair, a lot of the new HPs have the ‘Quiet Mark’ but that’s nothing official from a regulatory perspective.

Wholeheartedly agree. Same should be with the heat pump, the heat pump itself should be VAT free for whoever buys it, but for all practical purposes (HMRC admin) all the gubbins should only be VAT free if you’re getting as a supply & install job when retrofitting.

Get a heat geek to take a look, they’ll be able to sort the valve but also advise adjust the system to get the best out of it.

I would do your own heat loss, it's not super difficult but for mental bandwidth reasons, perhaps do it once you’ve done the weather compensation bit as @JohnMo described. Knowing that is invaluable and you can start to make very informed decisions without relying on variable quality tradesmen.

Those models have a MID approved meter inbuilt already as I understand it. https://www.ovoenergy.com/heat-pump-plus

What ASHP do you have? If it’s a Valliant Arotherm Plus or a Viessmann Vitocal 15X you can go on OVOs Heat Pump Plus add on which is 15p/kWh for heat pump usage and that doesn’t have any special times so you can run its low, slow and steady for maximum SCoP and a cheap heat pump tariff to boot.

Good thread on it here too, which posted in another thread yesterday. https://energy-stats.uk/vaillant-arotherm-firmware-351-06-07-problems-energy-integral/amp/

Also, what’s the floor situation - concrete or suspended timber? If suspended timber, then there are relatively cheap* insulation opportunities there. Then you get the whole house wrapped up, rather than having a potentially cold floor. *vs digging up a concrete floor

Have you checked your firmware? https://energy-stats.uk/vaillant-arotherm-firmware-351-06-07-problems-energy-integral/amp/

The videos that convinced me were

I’ve got EPS beads retrofitted in my cavity walls. No issues so far. I wouldn’t trust blown fibre, as that can have a tendency to snag on the rough edges inside the cavity and cause clumping and then voids behind the clumps. Then you get cold spots. Beads on the other hand just flow and don’t really care about the rough edges and fill the space. Not only that, they’re not absorbent at all and the spaces allow water to fall through them (eg wind driven rain) and not across them to the internal leaf. Side benefit - it’s much quieter as sound doesn’t bounce around in the cavity. Didn’t realise about that until a few days after retrofit.

Avoid IWI if at all possible. Fill the cavity if possible (if there is one and not yet filled) with EPS beads. Then EWI. This assumes you’re going to have at least 300mm of loft insulation, and will top up if needed. To be honest, I wouldn’t bother with IWI anyway unless you’ve got some massive thermal bridges that need avoiding, as you probably won’t get the payback. I’d focus on the efficiency of the heating system, getting the lowest possible flow temperature possible to get the highest SCoP. But that’s just me.

This.

Doh yes 5.5kW, not 9.5kW! And mad they’re specifying such a large HP!

If there’s scope to increase the loft insulation to 300mm if not already and fill the cavities with EPS beads then do those first. 9.5kW for 70m2 seems awfully high. I’d be interested to know how much of that is assumed ventilation losses. Also yes that’s a high flow temp, very painful. Most of those emitters seem like the minimum they can get away with. I’d be asking them to calculate for 40c flow, and only if the emitters *cannot* be done sensibly, then increase the flow temperature from there. Also, they can get creative having multiple emitters in a room rather than one big one and also going up to 700mm rather than 600mm etc. Lots of ways to skin the cat.

If you’ve got around 1ft in the loft that’s probably fine as long as there’s no obvious gaps in the insulation layer. Definitely get your cavity walls checked and if they’re unfilled or partially filled, get them filled with EPS beads if possible. Airtightness is the other large thing that needs resolving, making sure there’s no gaping holes apart from intended ventilation. Do / get a heat loss survey, there’s a calculator in the forum that’s good or you can use heatpunk online but basically you measure every wall, door, window and assign each element its u-value (how insulating it is) and ventilation losses(blower door test) and it will then tell you your heat loss is at your design temperature (usually -3c outdoor or something, specific for your location). The heat loss results drive everything - cannot stress how important it is to know. Indeed to give an example, one of my close friends considered upgrading a new external door, some other invasive insulation install as they were cold basically. I did the heat loss survey, basically they have tiny tiny radiators that cannot output enough heat even on their gas boiler system at 70c flow temperature. Insulation wasn’t the problem. I recommend a heat geek, https://www.heatgeek.com if you’re unsure, but if there’s a trusted local heating engineer that’s reputable also go them for a heat loss survey.

In addition to the loft insulation question, what’s the floor make up is it concrete or suspended timber?

I’d agree with the above. Don’t sweat it, yes it’s not *the* best, but it’s not a big deal. Continue the focus on airtightness in the remaining build, and the design of heating system to counter it by being really efficient.

Pro Clima Solido SL tape with the wall sprayed with SPrimer before taping. Not cheap, but excellent stuff.

Ah I’ve been looking at them for cooling as part of my ASHP plan for next year. Hopefully the build quality is decent?

Making my ground floor windproof & insulated (as much as realistically possible in retrofit) has made the world of difference. Along with MVHR has been one of the best investments I’ve made.

Yeah exactly the same! I opened the fused spur and removed the LS and same on the MVHR side. Worked straight away and now living my best MVHR life. 🤪

I’ll just leave this here. https://www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors

Can’t quite tell, but the pictures look like there are was some fairly sizeable gaps between the floorboards and the wall. If that’s the case I can imagine lots of cold air being blown up on a breezy day. Possibly a major contributor to rotting the bottom of the woodwork if warm vapour is condensing on the cold wood.