SBMS

Where in the country are you based?

We've done a lot of research into ASHP for our self build, and I think it's a really difficult topic to approach because there's a huge amount of noise surrounding people's perceptions of "MCS Certified installers". I've been converted from looking at LPG for our off grid self buil, doing a tonne of research into ASHP, upping my build insulation spec and settling on ASHP. However, I keep seeing the same comments regarding 'inflated' prices for MCS certified installs of ASHP (that offset any incentive schemes such as RHI, or BUS). Maybe that's some people's experiences; it's not been mine. I'm also not sure why this particular element of self build people are happy to either DIY install, or give to a yellow-pages plumber, as if there are no expertise involved in the design and commissioning of a system. There doesn't seem to be the same approach to other skilled areas of building (such as foundations, or roof construction!) Firstly, what I would say is that, in my opinion, an MCS certified install should be worth its money, when considering the "Boiler Upgrade Scheme" grant. With the greatest respect to commenters like @markc ("Don’t bother, why pay more than £5k over the odds to get £5K back.") - this has not been my experience from getting quotes, and it shouldn't be anyone else's. If it is, you've found a dodgy installer and you should try someone else! But I don't think a few bad apples should spoil the bunch. The links that I've seen time and again for ASHP DIY (or 'bring your own plumber') installs are - a 2k ASHP, a 1k Cylinder, Maybe a buffer (who knows) and no mention of pipework, electricals, labour etc. So on this basis, at a first glance you might think "well I can install a properly sized, warrantied ASHP for £3k - maybe 3.5k including the plumber's labour". I'd challenge that. Most quotes we've received back from MCS certified installers are in the 10k-11k region. Picking that higher end 11k quote, that can be broken down to: Nibe 2040 12kw Air Source Heat Pump Nibe 300L Heat Pump Cylinder 100L Buffer SMO20 Controller Nibe VST 11 Valve Nibe HR10 Valve Pipework MCS and Commission of System So this system, after the BUS grant of £5k will cost us £6k. For reference, the Nibe heatpump retails at around £7k. Let's assume installers can pick that up for 5k-6k. It's in a similar price range for Ecodans, Panasonic and Samsung units. I appreciate the Nibe is a more expensive unit, but I'd really question a price differential on the unit of £4k - can we really say that we're comparing apples with apples when we're pitching an MCS, 7-year warrantied install with what you can pick up on ebay? By my reckoning, you shouldn't be paying more than £11-12k for an MSC Certified ASHP install, and in my view, after the BUS grant of £5k that system should be costing you the same as the installed heat pump. So you should look at the grant as providing a cylinder, buffer, controllers, commissioning, pipework, labour, MCS Certification and 5-7 year warranty for 'free'. Just my 2 cents worth.

This might have been asked before but speaking to a number of companies it seems they recommend a branch system with rigid ducting versus a radial with semi rigid? For those who have installed MVHR which route did you go down?

Thanks all - makes sense. Just wanted to make sure these were normal, good to hear they are.

Thanks for suggestions everyone.

Thanks will look them up!

Thanks @nod Lancashire, north west

I know lots of members are keen to DIY install MVHR - and we may go that route. I wanted to ask though if anyone had used a turnkey supplier and installer for MVHR that they could recommend?

Standard brick and block on dense clay, so nothing unusual. SE has specified 750mm wide foundations. There are a few things that I think are over specified by the SE but wondered if anyone else had experience of 750mm strips?

Also you mentioned your mortgage broker has suggested buildloan. Just to clarify, buildloan are a financial intermediary - not a lender. It’s actually buildstore that we went with and they hand off to their sister company buildloan. Buildstore are a mortgage broker and I would suggest, if you’re looking at using buildloan, you use buildstore to package everything up.

We used buildloan. They were great and the mortgage broker was really good and got back to us with things like decision in principle within 48 hours. They fully understood how to present us to lender as am technically self employed with own company. Was able to pick the best lender based on how our income was assessed. We also opted for an advance stage mortgage which means funds are advanced prior to a certain stage being started - rather than a valuation and (hopeful) uplift at the end. Completely down to your appetite for risk and we paid a £4000 premium for ‘build out cover’ that goes hand in hand with the advance stage mortgage. Build out cover is for the benefit of the lender and is basically an insurance policy that pays out in the event we default and provides lender the funds to finish the build on our behalf and recoup their lending. For me (and I know others will disagree) there’s enough risk in a self build without the worry whether your foundations have increased in value to the tune of what you’ve spent. So 4K was a reasonable price to totally mitigate this risk and mean we are always in theory cash flow positive during the build. Obviously if you’ve loads of equity, cash, or own plot outright this isn’t relevant! But for us, buildloan have worked out well.

Lancashire - brick and block with 150mm blown eps cavity.

We have recently had quotes back for our self build for those that are interested. 250sqm house plus detached garage and we are coming in at around £1650 per sqm. That’s a good spec, ASHP, MVHR, well insulated and with a healthy 35k budget for the kitchen. Ours has some complex bits with 15k of steelwork, and 2 different ridge heights on roof meaning loose lay with about 3 weeks of joinery building the roof, which added to cost considerably. This is priced for a main local builder/ contractor and clean feet. Just in case this is of interest and this has been priced this week with 2022 prices for everything (which has pushed budget up considerably from last year when we did our budget).

Thanks @Iceverge

Would you recommend a particular EPS bead product?

We are looking at a brick and block construction with a 150mm cavity. What experience has everyone got with the above option and can anyone recommend a particular insulation method for a 150mm cavity? At the moment am favouring a blown in product as it’s guaranteed 100% coverage but would be interested to hear peoples thoughts on price and performance?

In a traditional brick and block construction what’s the consensus on the main areas where airtightness can be lost? Our SAP guys have gone for an air change of 4 which is clearly higher than I would like. With well fitted doors and windows, warm roof and plasterboard on dot and dab, what sort of a difference might we expect with a well built shell? I know recommendation is wet plaster and parging between floors but I wondered if there are any real world examples from members where dot and dab and no parging were used?

@joe90 Can you share your Air permeability test/changes per hour?

@Iceverge Quickly read the mentioned topic, but what's the rationale in a nutshell? If you have a good builder who can fit PIR well onto the inner leaf is there any reason you would still recommend full fill mineral?

@ProDaveThanks, that makes sense. The coldest day value (+20, -10) is coming out at around 7776 (7.7kW), average is around 4.1kW. A worst case scenario for an ASHP generating 184kWh of heat in a 24hr period, would be 61kWh of electricity (or £12). Thats a whopping bill of £380! But I guess this is extremely unlikely. I also don't think Jeremy's spreadsheet makes a huge amount of sense for summer values? i.e. we never have any central heating on from around May to September, so in theory there's a 0kWh requirement in these months, but this isn't what the spreadsheet is showing. Is that typical with an ASHP too? Also - am I right in thinking that a worst case of 7.7kW would require an 8kW ASHP?

Just thought I'd send some appreciation for his work on it.

Hi all Thanks @Jeremy Harris for your useful calculator. I'm just trying to get my head around some of the numbers so we can assess different insulation levels, double vs trouble glazing etc. I just wanted to make sure I am reading the calculator correctly! I've plumbed in the following values: Air changes per hour = 4 MVHR efficiency = 85% Wall U value = 0.19 Floor U value = 0.1 Roof U value = 0.16 Average window U value = 0.8 Average door U value = 1.2 Average roof light U value = 1.3 Along with the following dimensions of our property Internal wall area = 272.00 m2 Internal roof area = 125.00 m2 Internal floor area = 128.00 m2 House total internal volume = 700 m³ Its a 2.5 storey house, 240 total square meters and I've used an online calculator to ascertain the internal volume using our working drawings. It appears to be generating a space heating requirement of 23,933kWh per annum for average OAT (the sum of row 84). This is giving an average cost per square meter to heat of about £100. This seems really high, but perhaps I am misreading or misunderstanding? I am effectively trying to work back from this to understand the electricity costs for an ASHP to heat this space. It seems that the "Total daily heat loss power for average OAT (W)" is coming out at 4109W (4.1kW), but then it seems that this value is multiplied by 24, so I'm assuming this isn't the total Daily heat loss power, but the total Hourly heat loss power? Thanks in advance.

Got you. So effectively they're going off some 'stock' figures. I was going off ecotherm's calculator; https://uvaluecalculator.ecotherm.co.uk/calculator/walls/cavity wall/brick/lightweight (0.15)/3mm skim-coated 12.5mm plasterboard/partial fill/75/ which is the manufacturer @ our local merchants. Kingspan's calculator has a lower mark of 0.18 - both of these are better than the U Values used by the SAP calculator. I assume these would suffice as evidence?

This is the SAP calcs done by a firm, based on the above spec... Are you saying that they don't adjust the 'As Designed' Spec, to reflect the cavity solution described above?

Hi all We have received our first set of SAP Calcs back for our new build. The wall U-Values are coming out around 0.22 - this is using 100mm block, 100mm cavity with 75mm PIR, 100mm inner light block (just standard for now). However, putting this same spec into Kingspan/EcoTherm U-Value calculators, it spits out 0.17. Does the SAP Software calculate things differently? Thanks