WisteriaMews

I've just completed the survey. Any follow up questions let me know!

Build cost - I don't think £3,500 per sqm is that crazy in the south east if you are going to do a decent specification (e.g. you mention a lot of renewable tech). Build costs have gone up a lot post pandemic. I actually think it's refreshing they've given you an estimate (many architects don't in my experience). I'd suggest an open conversation with them on why they think that will be the cost They'll know the cost of their recently completed projects. I expect they have some comparable projects to yours that have cost £3,500 per sqm and that's why their suggesting that price to you. Architect fees - in my (limited) experience all architects base their fees on a % of your project cost. Stage 0-3 they usually price on a % what you say your budget is. When it has become clearer what the real cost is going to be they'll re-baseline for the later stages. There will be a lot of work in a 441 sqm building. It's really tough. It's a lot of money. It feels very frustrating when you get fee hikes / estimates higher than you expected / hoped. I'm sure you can cut the build cost. Do you have time to fight for every bargain and do work yourself, or do you want to give the job to a good main contractor and take pressure off yourself? In my experience a good architect is really valuable on a project. They'll come up with good solutions, they'll design nice spaces to live in, they'll take a lot of work off you, they'll solve a lot of problems. (I suspect my view are contrary to a lot of people on this forum.)

If they've just asked for a warranty quote, rather than a proof of policy, hopefully you can just give them a quote. Similarly can you just give them a solicitors details, but tell the solicitor not to do any work until you give them the green light.

*penultimate bullet point should say "buy the new build warranty before you commence work...."

It would probably be best to speak to a self build mortgage broker as they'll be able to offer some advice on your circumstances (e.g. Buildstore - not recommending them, but they are one of the bigger players in the market). The Buildstore website has into on it how the process works too. Generically I'd say: - I'd hope you can get an in principle mortgage offer without having to pay any fees. - Knowing that the mortgage looks 'do able' depending on your approach to risk you could then get a QS / costing to price your build, to know if the house you want is achievable within the amount you can borrow. - if happy, press go on the mortgage. Conveyancing, mortgage fees, stamp duty etc.... all kick. The mortgage doesn't cover these. - Once you have the land, you need a bunch of professional services; architect, structural engineer, soil survey, discharging planning conditions, building control, etc... Your circumstances will determine how many of these you'll need (you can never avoid them all). I've not seen a self build mortgage that will release funds to cover these fees. - In my experience you need to buy the new build before you commence work (as they send an inspector as you go along). - Unfortunately there are lots of outgoings before you start building!

Currently planning for our next self build. We are doing to have an electric heated towel radiator in all the bathrooms and I'm looking for a controller to meet our two requirements: 1. Ability to set a schedule via WiFi / an app. 2. A physical boost button that we can press to turn the radiator on for an hour / two hours. For the times when you have a shower outside of the scheduled times and want to turn the radiator on to dry the towels by just pressing with a button and not needing to faff with a phone / tablet. Can anyone recommend a controller like this?

@TerryE thank you for the detailed reply. I'm not as IT savvy so the above is probably a bit advanced for me! 🙂 Might be a silly question, but how.did you install the top and bottom thermometers? I'm assuming they are on the outside of the tank? Did you try to get round the insulation to install them on the metal skin of the tank? It sounds like you only use a top temperature sensor to drive the boost if needed? Being able to have a boost is my main concern, so I might be able to do something simpler than your setup. (I'm planning to be on Go / Flux rather than Agile so will have a set block of off peak that I can just use a timer for.)

@TerryE @JanetE I'm looking to specify the same tank in my new passive self build, but have been struggling to find out many specifics about the controls. Ideally I think I'd like to: 1. Heat to full overnight on off peak electricity - it sounds like it has timers so this should be possible. 2. If the tank falls below a certain level boost it so there is enough hot water for evening showers / so we don't run out etc... - I haven't been able to find anything on a 'smart' feature like this being possible. Are you able to share your experience with the tank controls. Thanks.

PHPP tells us it's sufficient. Still feels like a bit of a leap of faith installing such a low power system.

Yes, our architects are Passive House qualified.

We're planning a certified passive house and are looking to install a Zhender ComfoAir Q450 with the Zhender Comfoclime bolt on that does heating and cooling. Assuming we hit the passive house standard, that should be sufficient for us. I see you mention above UFH (and also have seen your other post about ASHP), if you get a heat pump that can reverse you could do both via the UFH; heat the slab in winter and cool it in summer.

Not much further forward, currently waiting for the structural engineer to finish a few pieces before we can fully engage a timber frame suppliers. We're in London.

If you are happy with them, could you share who supplied your external blinds? I think we'll be installing some as well.

Thanks for all the info. We are looking at an Oso cylinder having seen it mentioned on the forum.

Our architects are doing the PHPP modelling so I'll ask them for the cooling load. We are currently aiming to be certified.

The MVHR design / modelling we've had done shows 229 m3/h or 286 m3/h on boost. The Zhender data sheet (thanks for the suggestion to double check all this) shows 1.1 kW of cooling at 315 m3/h, so we'd probably get ~1kW on boost. Possibly not enough..... What types of intervention do you use on hot days?

I'm pretty committed to getting a panelised system from an experienced passive house supplier. There are no experienced passive house builders near me, and I don't have a relationship with a building company who are committed to getting into passive houses / getting it right, so I see a panelised system as a lower risk option. We self built our current house and despite using a 'good' local builder, I've been disappointed with the thermal result (air tightness / thermal bridges). This has definitely influenced my decision for our next project.

Not ideal! Our architects emailed them around the time we got planning and they gave us an estimate and seemed reasonably responsive then. We're now at the stage of getting more serious and working out the finer details with the front runners.

I realise this is a slightly "how long is a piece of string" question.... We are finalising the technical design / specification for our passive house and are keen to install some cooling, to counter the over heating days and effects of global warming (as best we can). PHPP will tell us our heating demand (e.g. 10W/m² heating load), but I'm not aware of it giving a cooling load. We are considering a Zhender MVHR with Comfoclime 36 add-on that can provide 1.7 kW cooling capacity and 2.2 kW heating capacity. Has anyone got any advice on whether that cooling capacity will be enough? We're currently also finalising the external shading, but intend to have shading to stop the house getting too hot in the first place.

Has anyone used White Haus (https://white-haus.com/) for their timber frame? They are one of the front runners for our passive house project and we were looking for feedback from anyone that might have used them / considered them. They seem to be one of the lesser known timber frame suppliers and are part of the Intelligent Membrane / Passive Purple group of companies.

I've spoke to a couple of warranty companies and they told me there were no special requirements for covering a basement. However, it seems to be standard that they don't cover water ingress (which is why they don't insist on an insurance backed guarantee). We're looking at Type B & C waterproofing on our basement. If anyone has any recommendations of companies they've used please let me know!

We having planning for a self build passive house that includes an 81 sqm basement. We've had for quotes for the basement and the most affordable one is from an old school groundworks / basement company that will build the box but don't do waterproofing so we'll probably get that done separately, using Type B & C. I had a couple of questions I'm hoping the forum might be able to help with: 1. We'll went a new build warranty with the house. Are there any warranty specific requirements for a basement? We've got an experienced structural engineer on board, it will meet building regs etc.... For our current self build, our warranty required us to get an insurance backed guarantee on the flat roof install. I'm guessing the warranty provider will want an insurance backed guarantee on the waterproofing. Is there anything else? I plan to call a warranty company as well, but would appreciate the thoughts of anyone who has been through the process. 2. Any advice around organising our own Type B & C waterproofing? I'm assuming we'll need a firm to design and install it (or to use one of the design firms approved installers) so that we get an insurance backed guarantee. Any recommendations of firms (I'm south east London based)? Indications of what it might cost? Thanks.

Are you running the tank purely from solar / grid electricity, or do you have it connected to an ASHP. We have planning for a passive house and I was thinking of a Sunamp, but have been put off by all the stories and the price, so am now thinking of an OSO running from solar / off peak grid electricity.

All of the quotes were from planning drawings. That's one of the reasons I expect the quotes to go up when they get to building regs and the lintels required over openings etc ... Per @TerryE you need to be aware of cladding costs. We're looking at a mix of metal standing seam and charred timber and it is looking like it will cost not much less than the timber frame installed.

I received some quotes before Christmas from 3 frame suppliers, including MBC, and the average was £800 per m2. The advice I got is that these were initial quotes and when you got into the detail of adding the necessary structural elements (e.g. the odd steel) it would nudge up a bit.