miike

I spent some time putting together the differences battery size makes when paired with different PV systems. It varies quite a lot on the PV kWp and also whether or not you have an ASHP. Figures used for PV/Battery costs are from here 1. This shows the gain from PV with no battery and no ASHP 2. PV, no battery, with ASHP 3. Battery sizes (5, 10 and 15 kW) paired with different PV kWp. No ASHP 4. Battery sizes (5, 10 and 15 kW) paired with different PV kWp. With ASHP 5. Ranked by cheapest cost (total cost of PV + Battery) per SAP point gained. No ASHP 6. Ranked by cheapest cost (total cost of PV + Battery) per SAP point gained. With ASHP

Elmhurst Energy, there's a 14 day free trial here but the actual license fee isn't too bad. I think they took over Stroma, which was who I'd seen recommended here previously.

SAP 10.2, it's the latest version used for all post 2022 builds.

Yes, took ages copying all the details into the new one before making changes. That 100% isn't for efficiency, it's for percentage of heat i.e. how much of the heating for the house is done by that unit (for situations where you have multiple sources).

This is all done on the latest SAP 10 standards. I've attached some screenshots showing the score change from making one alteration to the spec, leaving all else the same. I reset the spec to the original before changing a new data field. I start on 87 B with no ASHP or MVHR, 0.15 u for roof and 0.1 u for walls. Air Tightness - no change in score between 6.60 and 0.10 Roof u-value (251m2 gross area) - 1 point change between 0.35 u value and 0.05 Adding MVHR - 5 point reduction to 82 Adding 6kW PV + 12 kWh battery - increase of 8 points to 95 Changes to data but keeping the PV and battery in the spec: Main heating source changed from mains gas to ASHP - 12 point reduction to 83 Flat roof u-value - improving u-value from 0.15 to 0.1 has no effect. Worsening the u-value to 0.7 drops the score by 3 points to 92

My design SAP used a lot of standard assumed data, such as double glazed windows, no MVHR, gas boiler, numerous openings for air extraction etc. It had a score of 87 B. The actual build used significantly more insulation, 3G windows, MVHR, ASHP. The costs of the upgrades would be in the tens of £ks. After submitting all this info, my energy performance was downgraded to a C with an 8 point drop to 79. I thought the assessor must be entering something wrong so I got access to a trial version of SAP assessment program and re-did the info myself. Nope, it somehow actually gave me an even lower score of 73. I removed the MVHR and added vents, changed the ASHP to a mains gas boiler and straight back to 87. I understand how these can drop a SAP score because it focuses on electricity costs and these are electric devices, but it was interesting to see that none of the other improvements moved the needle by a single point. Out of curiosity, I started playing with some of the data and gave it an air tightness score of just above 0 and boosted the u-values of all the materials - I managed to get 1 additional point. The only thing that made any real difference was adding PV and a battery, which took it from between 93 to 100, depending on the kWh inputted. The lesson seems to be, if you want an A rating, is to keep everything standard, no 'eco' heating or ventilation systems, minimum insulation for building regs, and then just add a bit of PV. Might be useful for anyone needing to qualify for an Ecology mortgage.

I've got a lot of left over PIR insulation boards, enough to fill a 12 yard skip, and have being trying to think of a possible way they could be used instead of paying £500 to just bin them. They're an awkward mix of sizes, tapered, and cuts, so selling them would be tough. At the same time, I have a sloping garden path which needs c400mm of backfilling. The ground is sandstone. Would there be anything problematic about laying some of the boards down first, prior to filling with the remaining aggregates? It would halve the amount of aggregates I'd then need to use. I've heard of people using PIR boards under soil in planters, to insulate the plants during the winter, so I assume they have some garden utility.

It's a full new build, so no existing heating system. It's also reasonably well insulated - I've been monitoring the internal temperature and it seems to lose 1C overnight, with a 10C difference in external temperatures. The issue I have is size - it's c5500 sqft. Hybrid system is an interesting suggestion, I've already connected gas so could definitely be an option. I'll have a look into that.

You're right that a used unit is probably not worth the hassle. Issue I have, is that I need a min 15kW unit and 300L cylinder, which gets on the more expensive side of units. I've written off the grant as just covering labour install, so I still have £7k+ of supply costs. Has anyone ordered units from Alibaba before? I recognise a few units which are rebranded in the UK but are just imports from the same manufacturer in China. I've ordered a lot through Alibaba in the past for work and the hardest part is knowing which company to trust and buy from.

I'm struggling to get a firm answer on this, but does anyone know if the gov ASHP grant would still be paid out if the pump you install was preowned? My plumber said that as part of the grant process, he registers the unit with them before they pay out the grant. The issue that I can see arising here, if the unit is preowned, is what if it had already been registered by the previous owner to get the grant? My plumber was unsure, and I can't find any specific details relating to this. Has anyone had any experience with this situation?

I got a DeWalt heavy duty stapler that has no issues going into OSB. It requires quite a bit of pressure to use though, which you can certainly feel after a few thousand staples.

Does anyone remember 2-3 years ago the Tories had a similar plan to increase building and cut red tape - and then they immediately lost some local elections in response to the plans so they completely backed down on them? And they're the party that gets a substantial % of their donations from house builders. I can't see a different pattern playing out with Labour as at the end of the day, the only thing that really matters is votes and c80% people who are 65+ vote vs just over 50% of people under 34. And nothing unites the older demographic of the UK like opposing new homes does.

I wonder how CIL liability and commencement works if it's extending an already existing house - you have 3 years to start from pp but what if you want to do other permitted development works first? Maybe you want to replace the roof or other significant works. What if in this situation the home owner had responded that they hadn't commenced works on the CIL liable work, they're just doing a separate extension which doesn't require pp?

I feel like going underground is always easier with planning as no one can see it, so people care a lot less. I recently had a look at walk on glazing as there's a few areas I thought it would work really well - I then looked at the pricing and decided actually I could do without!

What is the sqm of the actual living areas? Looks to me like <50% of the 13k sqft is actual living space, with the rest as garages/courtyards/terraces. If I'm correct, then I think it could be built for a lot less than some of the above estimates. I recently built a not entirely dissimilar 3 storey house on a sloped site with 500m2 internal space + ~200m2 of terraces. The semi-submerged basement used two skins of blockwork, with a concrete filled cavity. The upper two floors were built with brick/block. There's about 75 structural steel beams. I would suggest looking at this method of construction rather than other more specialist types. I'd then approach groundworks companies and only provide limited drawings and ask to quote for specific sections - eg. the excavation, slab and blockwork for the basement floor. If you send all these drawings over then you'll probably get 50% added on to the price as they'll assume you can afford it based on the design. Excluding windows, I'd expect c£1m for building the shell of this house. You should budget for a lift though if you're going to have parking on the basement floor and the kitchen two floors above - it's quite a journey when bringing in grocery shopping.