NEWBIE eco self build

[ukjamie]

Hi guys, newbie here. Be great to touch base with like minded people, potentially picking your brains for and pros/cons you may have encountered on your building journey. We are just about to start an eco build, quite a large build with a pool. I work for a construction/civils company and have access to all plant etc, but never done a selfbuild, nor tried to claim back the VAT. So, any advice as to whom I should be in contact with, avoid etc would be more than welcome. Likewise, if I can off any advice, especially gong into the ground, I certainly will. Have a great weekend too

Edited September 3, 2021 by ukjamie

[markc]

Good morning and welcome. Loads of priceless information on here, try searching first and then ask away.

and I’m sure your knowledge of groundwork’s will come in handy.

[ukjamie]

Morning Mark,

 

yes, I have had a look at some of the topics and advice on this forum and it looks great. Just a bit nervous when I haven't done an eco build for myself whilst claiming back the VAT!

 

 

[IanR]

Hello @ukjamie and welcome

 

"Eco" build" conjures up all sorts of options. Are you sticking with the practical "low energy" options, or venturing towards earth homes or straw bale walls and composting toilets.

[ProDave]

ECO build and "pool" (with all the energy that uses) seems slightly contradictory?

 

Re the VAT, to start with just make sure the receipts for EVERYTHING are made out in YOUR name and keep them all safe in date order in a box file.  If you want to make your life easier (less paperwork in one go at the end) then download and print the VAT claim form now and fill it in as you get each invoice.

[ukjamie]

Eco build with a pool does seem contradictory, yes! Loads of solar, ground source heating, bore hole water...should save quite a bit on energy bills. No straw walls, just a timber framed build and dare I say, we are having air con too!

[ProDave]

2 minutes ago, ukjamie said:

Eco build with a pool does seem contradictory, yes! Loads of solar, ground source heating, bore hole water...should save quite a bit on energy bills. No straw walls, just a timber framed build and dare I say, we are having air con too!

That was tongue in cheek about the pool, if you want it then fine.

 

The pool brings it's own issues with humidity, but there must be a way to recycle excess heat from the pool room to help heat the rest of the house?

 

Research Ground source heat pumps before you commit.  Most find the extra cost of the ground pipes makes it way more expensive than an air source heat pump and the small extra efficiency will never repay the extra capital cost.  Also an ASHP will do cooling as well so no need for a separate air conditioning system.

[Bitpipe]

7 minutes ago, ukjamie said:

Eco build with a pool does seem contradictory, yes! Loads of solar, ground source heating, bore hole water...should save quite a bit on energy bills. No straw walls, just a timber framed build and dare I say, we are having air con too!

 

What low energy performance standard are you aiming for? Have you considered u values, airtightness, solar gain, MVHR etc..?

 

Correctly designing & building the fabric to minimise the heating and cooling requirement (both energy consumers) plus understanding how the house will perform year round will be key to delivering on your 'eco' objective. Be wary of 'green-wash' tech that make unrealistic claims and have a very long payback times.

 

Further to VAT comments above, you need to ensure that anyone who does work for you zero rates their invoices (you may need to provide your planning permission to satisfy them). You cannot reclaim VAT charged incorrectly on services.

 

You can only claim VAT for eligible materials bought by you, in your name, delivered to your address and you can only make one claim at the end of the project when the build is considered complete (e.g. BCO sign-off). Therefore to optimise your cash flow, the best approach is to get trades to supply & fit and zero rate at source.

 

 

[IanR]

16 minutes ago, ukjamie said:

...should save quite a bit on energy bills. 

 

16 minutes ago, ukjamie said:

just a timber framed build 

 

There's more energy to be saved with the spec of the timber-frame (and foundation) than with the renewables you choose to heat it.

What stage are you at? is the detail design done? Have you a view on an energy loss target for the building fabric? What spec of frame and foundation are you considering.

 

+1 for cooling via ASHP (or GSHP if your loads justify it). AC can be avoided.

[ukjamie]

12 minutes ago, IanR said:

 

 

There's more energy to be saved with the spec of the timber-frame (and foundation) than with the renewables you choose to heat it.

What stage are you at? is the detail design done? Have you a view on an energy loss target for the building fabric? What spec of frame and foundation are you considering.

 

+1 for cooling via ASHP (or GSHP if your loads justify it). AC can be avoided.

Ready to crack on. Footings and drains startingin a week or so. New concrete slab in 3 weeks and almost ready to press the button for the timeber frame manufacturers to start production. As for the ground/air source heating, I'm still a little in the dark as to how they can cool the house. do you have any knowlege of this?

 

[ukjamie]

18 minutes ago, Bitpipe said:

 

What low energy performance standard are you aiming for? Have you considered u values, airtightness, solar gain, MVHR etc..?

 

Correctly designing & building the fabric to minimise the heating and cooling requirement (both energy consumers) plus understanding how the house will perform year round will be key to delivering on your 'eco' objective. Be wary of 'green-wash' tech that make unrealistic claims and have a very long payback times.

 

Further to VAT comments above, you need to ensure that anyone who does work for you zero rates their invoices (you may need to provide your planning permission to satisfy them). You cannot reclaim VAT charged incorrectly on services.

 

You can only claim VAT for eligible materials bought by you, in your name, delivered to your address and you can only make one claim at the end of the project when the build is considered complete (e.g. BCO sign-off). Therefore to optimise your cash flow, the best approach is to get trades to supply & fit and zero rate at source.

 

 

I would love to achieve A rating! We have a great architect who does these designs/builds on a regular basis, so with his guidance we should gain a good rating. being a timber framed building should help wih the solar gain, but I am not 100% sure of all of this yet. Might have to get some of those old cloth snakes by the back door!

[IanR]

1 minute ago, ukjamie said:

Ready to crack on. Footings and drains startingin a week or so. New concrete slab in 3 weeks and almost ready to press the button for the timeber frame manufacturers to start production. As for the ground/air source heating, I'm still a little in the dark as to how they can cool the house. do you have any knowlege of this?

 

There's lots of knowledge on the forum regarding ASHP cooling via the UFH, and there's a few that additionally use fan chillers, cooled by the ASHP, for additional cooling in specific rooms.

I have ASHP cooling via UFH and it is effective.

GSHP can be more efficient than ASHP with cooling since their medium is already at a lower temperature (8°C - 10°C), so can offer cooling without the compressor running.

Finding installers confident with ASHP/GSHP Cooling can be difficult.

What's the spec of your timber frame? Are you going with traditional founds? have you taken any steps to mitigate cold bridging, beyond standard building regs?

[ProDave]

To achieve EPC A is not straightforward for an "ordinary" timber frame.

 

I have just competed my new house, typical wall roof and floor U values 0.14 or better, triple glazed windows all with Uw <1 typically 0.9, 5kW ASHP for heating and DHW and 4kWp solar PV.  ventliation by MVHR. That achieved an EPC of A94. 

 

I doubt you would get to A without the solar PV and air tightness will play a big part in the energy efficiency (and will need tested) so attention to detail to make the whole build air tight is key.

 

I am not sure how the pool impacts the EPC rating, perhaps @AliG could comment I know he has a pool.

[ukjamie]

5 minutes ago, IanR said:

There's lots of knowledge on the forum regarding ASHP cooling via the UFH, and there's a few that additionally use fan chillers, cooled by the ASHP, for additional cooling in specific rooms.

I have ASHP cooling via UFH and it is effective.

GSHP can be more efficient than ASHP with cooling since their medium is already at a lower temperature (8°C - 10°C), so can offer cooling without the compressor running.

Finding installers confident with ASHP/GSHP Cooling can be difficult.

What's the spec of your timber frame? Are you going with traditional founds? have you taken any steps to mitigate cold bridging, beyond standard building regs?

Do you find the ASHP can cool the floors sufficiently during mid summer? Not sure how that works but very interesting.

 

As for the timber frame specs...? But the design has no traditional founds and the cold bridging in the walls at least, will be fibre board insulation. 

[ukjamie]

4 minutes ago, ProDave said:

To achieve EPC A is not straightforward for an "ordinary" timber frame.

 

I have just competed my new house, typical wall roof and floor U values 0.14 or better, triple glazed windows all with Uw <1 typically 0.9, 5kW ASHP for heating and DHW and 4kWp solar PV.  ventliation by MVHR. That achieved an EPC of A94. 

 

I doubt you would get to A without the solar PV and air tightness will play a big part in the energy efficiency (and will need tested) so attention to detail to make the whole build air tight is key.

 

I am not sure how the pool impacts the EPC rating, perhaps @AliG could comment I know he has a pool.

thanks Dave. 

 

We are gong with triple glazing throughout and the timber frame designers (Inspire) asure us of the 'air tightness' will be excellent. Lets hope so. The MVHR system is still on the design table but if we decide this, it will obviously have to be incorperated in the timber frame design. We have an 11m RSJ going across the kitchen patio door that won't hlp with the ratings either.

 

 

[ProDave]

10 minutes ago, ukjamie said:

thanks Dave. 

 

We are gong with triple glazing throughout and the timber frame designers (Inspire) asure us of the 'air tightness' will be excellent. Lets hope so. The MVHR system is still on the design table but if we decide this, it will obviously have to be incorperated in the timber frame design. We have an 11m RSJ going across the kitchen patio door that won't hlp with the ratings either.

 

 

Am I reading that right, an 11 metre RSJ over a window / door opening.

 

That is a subject in itself, that is a seriously big span and a seriously large joist that is probably going to have a big deflection.  Think long and hard about that aspect of the design.  Also that will be a lot of glazing to lose heat in the winter and over heat you in the summer.

[IanR]

32 minutes ago, ukjamie said:

Do you find the ASHP can cool the floors sufficiently during mid summer? Not sure how that works but very interesting.

Yes...but... I have low heat loss/gain, so for heating only require a low flow temp. For a 21°C target temp, I have around a 31°C flow temp and keep the slab at around 21.5°C. 
ie. the slab temp only needs to be slightly above the desired room temp.

 

For cooling, similar offsets are required. ie. I take the slab down to around 19°C with a flow temp of around 14°C (avoiding dropping below the dew point and causing condensation problems)  and it keeps the indoor temp stable.

The caveat is, that with a low flow temp heating system it is slow to react, so you can't wait until it is 27°C degrees in side before taking action on cooling. And for me, because I chose to have a fair amount of glazing on south-east and south-west aspects, I need to mitigate the solar gain risk, which I've done with external shading.

AC does have a quicker effect on cooling, as it works directly on the air temp, but as soon as you switch it off the temps will rise again as you are unlikely to have significantly lowered the temp of the building fabric.

If I was doing mine now, with the knowledge gained from this forum, I'd be considering adding some fan chillers cooled by the ASHP to get the same quick benefit as AC, while still getting the stabilising effect of the UFH cooling.

When I was asking timber frame specs, it was in relation to being an "eco build". ie. what level and type of insulation and what air tightness target.

I have an I-Joist structure with 300mm walls and 350mm roof, filled with cellulose fibre insulation and sitting on an insulated raft foundation with no cold bridging, and a sub 0.1 ACH air tightness. Nothing high tech at all, nor particularly expensive, but good value for the energy losses it delivers.

If you drop below 3m³/m²h @50Pa buiding regs will require you to have mechanical ventilation.

Edited September 3, 2021 by IanR

[ukjamie]

4 minutes ago, ProDave said:

Am I reading that right, an 11 metre RSJ over a window / door opening.

 

That is a subject in itself, that is a seriously big span and a seriously large joist that is probably going to have a big deflection.  Think long and hard about that aspect of the design.  Also that will be a lot of glazing to lose heat in the winter and over heat you in the summer.

you did read that right Dave. It has been designed and thought through but the wife is adamant (see how I blamed her) this is the degin she wants. It is a big place we are building, so it wont look too out of place. And yes, we will lose loads in this area!

[ukjamie]

4 minutes ago, IanR said:

Yes...but... I have low heat loss/gain, so for heating only require a low flow temp. For a 21°C target temp, I have around a 31°C flow temp and keep the slab at around 21.5°C. 
ie. the slab temp only needs to be slightly above the desired room temp.

 

For cooling, similar offsets are required. ie. I take the slab down to around 19°C with a flow temp of around 14°C (avoiding dropping below the dew point and causing condensation problems)  and it keeps the indoor temp stable.

The caveats is, that with a low flow temp heating system it is slow to react, so you can't wait until it is 27°C degrees in side before taking action on cooling. And for me, because I chose to have a fair amount of glazing on south-east and south-west aspects, I need to mitigate the solar gain risk, which I've done with external shading.

AC does have a quicker effect on cooling, as it works directly on the air temp, but as soon as you switch it off the temps will rise again as you are unlikely to have significantly lowered the temp of the building fabric.

If I was doing mine now, with the knowledge gained from this forum, I'd be considering adding some fan chillers cooled by the ASHP to get the same quick benefit as AC, while still getting the stabilising effect of the UFH cooling.

When I was asking timber frame specs, it was in relation to being an "eco build". ie. what level and type of insulation and what air tightness target.

I have an I-Joist structure with 300mm walls and 350mm roof, filled with cellulose fibre insulation and sitting on an insulated raft foundation with no cold bridging, and a sub 0.1 ACH air tightness. Nothing high tech at all, nor particularly expensive, but good value for the energy losses it delivers.

If you drop below 3m³/m²h @50Pa buiding regs will require you to have mechanical ventilation.

great advice thanks Ian. I feel the need to revisit the air con decision and loom towards the fan chillers.

[Nickfromwales]

14 minutes ago, ukjamie said:

and the timber frame designers (Inspire) asure us of the 'air tightness' will be excellent. Lets hope so. The MVHR system is still on the design table but if we decide this, it will obviously have to be incorperated in the timber frame design.

Hi and welcome to the forum. 
From what you’re saying here, and above, you may already have the horse and the cart the wrong way ‘round  

MVHR cannot be ‘on the table’ if the intention is to go for air tightness that is excellent. You’ll choke on your own fumes without MVHR, for one, plus to be “green” or “eco” ( terms often used very loosely, and more often with a complete lack of understanding of what that is supposed to deliver to you in this reasonably unique build ) you will 100% need to be actively recovering waste heat for re-introduction through the MVHR system! Building control will demand your as built air tightness ( ventilation / infiltration ) results to be sure you have adequate numbers of air changes per hour. If all the above is known, how do you propose to meet those requirements? Make the house AT and then fit loads of trickle vents? ?. 
All these questions need firm and robust answers BEFORE pressing ANY more buttons.

I’m currently providing M&E for such a dwelling ( pool etc ) and the design work was enormous. The pool hall will need its own envelope as the dehumidification and heat recovery system typically runs at a slight negative pressure to preserve the build fabric, therefore it should not be able to ‘share’ the air volume of the residential section of the dwelling. Forget recovering heat from the pool hall, as every ounce of that will be absolutely needed to maintain the temps in the pool hall!! How big is the pool? Is it a pre-fab that you are “dressing” into the house 
Lots and lots of things here will impact on the others, so measure twice cut once ?

[scottishjohn]

how much insulation is going under your slab -is it sat in the ground?

 is it a complete insulated foundation ?

your final result will depend very much on  using a "frabic first approach" and that starts well before ordering TF kit and pouring slab-

any drawings will help the gurus direct you the right way 

Edited September 3, 2021 by scottishjohn

[pdf27]

2 hours ago, ProDave said:

Research Ground source heat pumps before you commit.  Most find the extra cost of the ground pipes makes it way more expensive than an air source heat pump and the small extra efficiency will never repay the extra capital cost.  Also an ASHP will do cooling as well so no need for a separate air conditioning system.

They arguably make economic sense if you need a ton of heating, where the improved efficiency in winter starts to save a reasonable amount of cash. Otherwise, it's very difficult to figure out ways where a GSHP is cheaper than an ASHP over the lifetime of the equipment. It's worth noting that for year-round heat loads (hot water and potentially a swimming pool), a GSHP doesn't add value: ground temperature is the same as the average air temperature where you are, lower if you start pulling heat out of it. That means if you use a lot of heat in summer 

 

We're looking at GSHP, but it's fairly special circumstances - heating load is small (2kW) so the cost differential isn't too big, our garden is big enough for the ground loop to go in trenches and I hate the aesthetics of an ASHP outdoor unit. Provided the cost differential can be kept down to a couple of thousand, GSHP is the better option for us. Playing around with spreadsheets suggests that the electricity consumption difference over the course of a year is probably within 100kWh or so however!

[AliG]

The pool makes no difference to the SAP calculation. It is just considered extra space.

 

You need to know the U-Value of the pool basin for the SAP calculation and that seems to be it.

 

When I ran the calculations I just considered it to be an extra room constantly heated to 29C as that is the water temperature. The heating cost aligns well with that calculation.

 

SAP does not take into account the use of energy for the pool pump and dehumidifier which I reckon is larger than the heating cost.

[Thorfun]

3 hours ago, ukjamie said:

Hi guys, newbie here. Be great to touch base with like minded people, potentially picking your brains for and pros/cons you may have encountered on your building journey. We are just about to start an eco build, quite a large build with a pool. I work for a construction/civils company and have access to all plant etc, but never done a selfbuild, nor tried to claim back the VAT. So, any advice as to whom I should be in contact with, avoid etc would be more than welcome. Likewise, if I can off any advice, especially gong into the ground, I certainly will. Have a great weekend too

Welcome. sounds like a great project. please share photos, drawings, designs etc. we love that sort of stuff. ? 

 

1 hour ago, ukjamie said:

great advice thanks Ian. I feel the need to revisit the air con decision and loom towards the fan chillers.

I'm going through this exact thing at the moment. quotes for AC are coming in at between £2k - £3.5k per room! so I've been reading a lot about Fan Coils on here and I know that @joth is going through some DIY experimentation with his at the moment and I am waiting with excited anticipation to hear about his results!

 

I also echo the above comments about taking a step back for a short while to decide what it is exactly you want and to investigate/design the MVHR now and consider insulated slab over traditional foundations etc. yes it will add a delay to your build and as I'm about 5 months in to my build and aren't quite finished in the ground yet (we're building a basement) I know all about how frustrating delays can be but sometimes they're unavoidable and the best thing to do. 

 

my experience so far is that things come at you thick and fast and you can easily get caught up in it all and miss important details.

 

good luck and we look forward to seeing the progress.

[ToughButterCup]

4 hours ago, ukjamie said:

... So, any advice as to whom I should be in contact with, avoid ....

 

Welcome.

'Waste time' on BuildHub. Often repays the effort. If nowt else is 'on' there's Good Sport to be had watching some of the regulars needling  Mods. Saints, all of them. ?