Custom Self Build (ICF, ASHP, MVHR, UFH)

[Merlolly]

Hi all,

 

My partner and I are just about to have our walls go up on our ICF low-energy (not quiet passiv)  three bedroom, two storey family house with a habitable attic. It's been a long haul to get to where we are with mistakes made, architect input both good and bad, lots of lessons learned. Found this forum a while ago but re-found it recently!

 

Basically, we're trying to achieve a decent sized house in a restricted plot within a village out of our price range to buy. Key drivers for our decisions were to build next door to the kids grandparents, keep running costs low while future proofing the design to accomodate our four young kidlings growing up rapidly in an evolving world!

 

A quick rundown on the systems we've got on the table:

 

ICF build system - Fully committed to the build system of expanded polystyrene blocks to be filled with concrete. The insualtion levels and zero drafts were a seductive choice early in the planning. Using a Scottish/Polish company to supply and install ICF walls while contracting the inital groundworks and future internal woodworks to a local reputable building company.

 

Air Source Heat Pump (ASHP) was our second choice of energy systems behind a ground source heat pump when we realised in October we'd never complete the build in time to qualify for the incetive ending in March. We'll take the boiler grant gladly instead   Not confirmed which model yet but have some in the running.

 

Mechanical Ventilation Heat Recovery (MVHR) - our mechanical venting system is fulfills two roles, keeping the houses escaping heat within the building envelope and cleansing the air for my allergy prone partner. System designed but not yet finalised on exact model. Intending to fit it ourselves with a little help from the manufacturer

 

Underfloor heating (UFH) - Wet underfloor heating on the ground floor. Something we'd always dreamed of! Plus it fits well with the other systems to keep the overall low enery input. Not sure on whether to use a anti-cracking matt, read many conflicting opinions.

 

Photo Voltaic panels and battery system - would love to have but our build budget just won't stretch that far. A real shame as we'll miss an opportunity to have integrated system but hey ho, you can't have it all.

 

As we've hit a few pitfalls in our journey, it's likely we'll be close to running out of money somewhere between being watertight and 1st/2nd fix so getting some advice and help around how to make our final budgeted funds go as far as possible would be awesome while we see our walls and interal woodwork go up over the coming months! Looking forward to posting some situations and reading more from the members here!

 

Also, more than happy to share our designs, ideas, trials and tribulations to those on a similar path or thinking about it

 

Cheers,

Merl

 

[Nickfromwales]

Hi, and welcome.

Some good choices there already so you're off in the right direction  

8 hours ago, Merlolly said:

A real shame as we'll miss an opportunity to have integrated system

On this point, just remember that a typical 4kwp system will absorb around 28m2 of roof space, so, for eg, if your roof covering is costing £100/m2 you'll have a hypothetical credit note of £2,800 gifted to you from the savings of not roofing that area. Maybe that helps to at least get panels on the roof and DC cables in at the time of roofing, with a view to connecting the remainder of the system downstream / when budget becomes available. 

[JohnMo]

Hi, do plenty of shopping around, as prices for the same item varies tremendously.

 

UFH is something you can design (using free software) and install yourself. 

 

ASHP various people on here have bought for an ASHP for a good price and local plumber and electrician installed, for many thousands less than an grant certified installer.

 

MVHR install plan well ahead for the installation, Posi joists are your friend.  Do not go flexible pipe or hard plastic pipe with tight bends.  Either metal duct or semi flex with inlet and outlet plenums (easy to install and quite), use 90mm duct to velocity of air low.

 

Above all, enjoy the journey.

 

Edited January 21, 2022 by JohnMo
Missed word

[Merlolly]

1 hour ago, Nickfromwales said:

Hi, and welcome.

Some good choices there already so you're off in the right direction  

On this point, just remember that a typical 4kwp system will absorb around 28m2 of roof space, so, for eg, if your roof covering is costing £100/m2 you'll have a hypothetical credit note of £2,800 gifted to you from the savings of not roofing that area. Maybe that helps to at least get panels on the roof and DC cables in at the time of roofing, with a view to connecting the remainder of the system downstream / when budget becomes available. 

 

Thanks Nick, glad to see so many people in the self build community!

 

Good point on the integrated design removing cost from the roof covereing - I'd discounted getting PV when our materials cost jumped up a big chunk last year. Worth looking into again and putting back on the table, thanks for the idea

 

[Merlolly]

35 minutes ago, JohnMo said:

Hi, do plenty of shopping around, as prices for the same item varies tremendously.

 

UFH is something you can design (using free software) and install yourself. 

 

ASHP various people on here have bought for an ASHP for a good price and local plumber and electrician installed, for many thousands less than an grant certified installer.

 

MVHR install plan well ahead for the installation, Posi joists are your friend.  Do not go flexible pipe or hard plastic pipe with tight bends.  Either metal duct or semi flex with inlet and outlet plenums (easy to install and quite), use 90mm duct to velocity of air low.

 

Above all, enjoy the journey.

 

 

Thanks for the thoughts and insights there John, all ideas and opinions welcome we're often finding it quite tricky to get like-for-like quotes so thanks for the reminder on how important that is to keep costs down!

 

UFH - the planning has been done on that one, free of charge! We're considering installing it ourselves as the labour cost seems extortionate but we're trying to weigh up that cost saving versus a guarentee from a certified installer. As I understand it, there could be future resale questions since repair/maintance is so costly? If you had any guidance on risk/benefits there, that would be gratefully received.

 

ASHP - I've seen a few articles on here, will get busy searching through threads!

 

MVHR - We've commissioned a design from ADM Systems which seems pretty decent - I'll drop a post in the MVHR discussion topic and would be keen to discuss further.

 

And yes, trying to enjoy it among the pressure of making 100s of decisions I never knew existed. Sometimes overwhelming but massively exciting when I remember to step back take it in!