Greetings for Buckinghamshire - Timberframe newbuild

[Zoo]

Hi All

 

So happy to be a member finally and a privilege to have access to such great resources.

 

Planning to build a 2-storey timber frame box of a home, 170m2, relatively air tight (around 1 air change per hour) with u values of 0.14 w/m2.

 

I've attached plans.

 

I'm totally green to self build, but eager to grow my knowledge and I'd like to put some basic questions out there if you could help.

 

In talking system for heating and DHW, my architect thinks UFH on the GF, radiators on the FF and a combi boiler is the way to go, which doesn't sit well for me for reasons I cannot fully articulate, only that I feel the architect hasn't started from a place that considers the performance of the buildings fabric before considering the options that would work best.

 

It'll  be a 5 bed home with 3 bathrooms and 3 of us occupying, but could be more occupiers in future and we'll often have people stay over.

We'll have mains gas. No attic space as it's a flat roof and a plant room on the GF.  A combi just doesn't sound adequate or am I out of touch? Has the combi boiler moved on?
I really didn't wan't to have radiators - though many look very lovely - will they be necessary at all or what are the other solutions so the wall surfaces can be flush and radiator-free?

 

We don't have tons of (money!) space for plant, just the utility room as I want to make the previously planned FF store for plant, a wardrobe for bed 5.

 

What do you guys think should be the plan of action?

If it is a generic, house non-specific route we go, are there better options than the combi boiler or is the architect spot on?

 

I also have questions regarding ventilation solutions, but I'll post them in a more appropriate forum.

 

Thank you in advance for any gems of advice or knowledge you may be kind enough to drop.

 

 

Zoocrib.pdf

[ProDave]

Hi and welcome.

 

You say it's 5 bedroom, but I only count 4, 3 upstairs and one down.

 

Which way is north and a plot layout would help?

 

My first comment downstairs is I would be using bedroom 4 as a snug lounge to escape the noise of a kitchen environment.

[jack]

2 minutes ago, ProDave said:

You say it's 5 bedroom, but I only count 4, 3 upstairs and one down.

 

See red writing on bedroom 2.

[SteamyTea]

Welcome.

Bucks is a nice county, have family there.

 

Rather than think about the heating system, have you looked into the energy requirements of the house.  Without knowing the heat demand it is hard to recommend anything.

You may find that improving the overall U-Value is cheaper and easier than a more complicated heating system.  Domestic hot water (DHW) and space heating really shoudl be kept separate, they do different things at different temperatures and at different times.

 

As you are having a flat roof, have you totally discounted having photovoltaics?  And how do you intend to get a 100% watertight roof?

 

[Zoo]

8 minutes ago, SteamyTea said:

Rather than think about the heating system, have you looked into the energy requirements of the house. 

That's the point I'm trying to articulate to my architect. Thank you.

 

I have just downloaded @JSHarris heat loss calculator and will plug in our values if this is a good starting point. But then what?

 

Have not discounted PV,  just thought they might be out of our league price-wise.

 

The EPDM roof will have a 12 degree slope and fully waterproofed with drainpipes and guttering.

[SteamyTea]

4 minutes ago, Zoo said:

But then what?

Then you look at all the heating options and decide.

The options can include air to water heat pumps, air to air heat pumps, gas, solid fuel (though not a good idea), electric (low capital cost).

[Zoo]

We'll have mains gas which is relatively cheap hence why the architect wants to use it. Combi boiler though?

[SteamyTea]

I am not an expert on makes and models of combi's, and being from a renewables background, not that pro them.

But from my understanding you get get some models that can modulate down, while still condensing (and therefore being more efficient) to a relatively low level.

With DHW you do at least know your minimum and maximum usage, so model choice is fairly easy.

And there is nothing to stop you having two boilers.

Edited May 9, 2018 by SteamyTea

[Zoo]

1 hour ago, SteamyTea said:

And there is nothing to stop you having two boilers.

The architect did say that! I should trust his judgement a little more

[PeterW]

4 hours ago, Zoo said:

The architect did say that! I should trust his judgement a little more

 

is he on commission to the boiler suppliers ....??

 

38kw combi will nail the dual showers but - and the big but - is you will need a decent water flow. You will then have an issue with needing a buffer for the UFH as the boiler won’t modulate down to give the floor flow temps directly. 

 

@Nickfromwales will be along shortly but you could go Sunamp PV for the hot water boosted by E7 and then a 5kw ASHP to the floor heating as I doubt your heating load will be above 3-4kw at most. 

[Zoo]

@PeterW Cheers for this information

[SteamyTea]

9 hours ago, PeterW said:

is he on commission to the boiler suppliers ....??

Probably not, it is the kind of 'sticky plaster' solution that an Architect will come up with.

 

My solution would be gas for the DHW and an ASHP for the space heating as that will probably deliver at the lowest CO₂ levels.

 

DHW really is a pain as you either have to deliver on demand and possibly suffer the lower flow rates or store and suffer the thermal losses.

The Sunamp does address the losses (as does a well insulated cylinder) and takes up less space.

[Zoo]

2 hours ago, SteamyTea said:

(as does a well insulated cylinder) and takes up less space.

Should I consider a UVC then? As I say, we’re not terribly flush for plant space.

[ProDave]

1 hour ago, Zoo said:

Should I consider a UVC then? As I say, we’re not terribly flush for plant space.

Yes.

 

But don't put it in the downstairs plant room / utility, that would put it a long way from the bathrooms.  Put it in the left hand single cupboard on the landing and have that as an airing cupboard. That will get the tank pretty central to the kitchen and all bathrooms and minimise the time taken for hot water to reach the taps.

 

I learned quite early in my build that "plant" is best distributed around the house as each item is best suited, so now the only thing in my "plant" room is the mvhr unit.

[SteamyTea]

Or no, if you want to install it yourself, it avoids the certification.

What are you doing about the very hard water in Bucks?

Fur up the heat exchanger and you may well be into a new thermal store.

I had so much scale in my cylinder it actually poked itself out the side.

[Nickfromwales]

22 hours ago, Zoo said:

The architect did say that! I should trust his judgement a little more

 Hmmmm.

 

Two boilers in a house with an ACH of 1 or less ?!?  . 

 

Decide if your going with PV before deciding anything else. It's a complete game changer for the space heating and DHW system design. 

 

You could go ASHP > UFH & ASHP > UVC and just leave it at that, but if gas is available I'd say use it. 

A decent high-flow gas combi will give 2 reasonable showers simultaneously, but they won't be blasting you for sure, but then you have nowhere to store excess PV generation. 

Sunamps are great for storage of PV / E10 and they're compact too, around 3-4 times smaller than the equivalent cylinder. Capital cost is higher, standing losses considerably lower, but in a passive level dwelling they can be the only wet heating device you need. 

Weigh up the cost of the gas install, standing charges, then you'll need a buffer tank for combi > UFH, or gas system boiler > thermal store ( TS will buffer the heating and provide DHW in one device ) plus annual servicing for life, life expectancy of the boiler and its service costs over 20 years and you soon have good argument to stay clear of gas unless you ABSOLUTELY need it. ( Cooking on gas is still achievable by using a single 47kG bottle of LPG ). 

PV or no PV, that needs to be decided first. . 

[SteamyTea]

I agree with Nick (on deciding if you go with PV)
.

What is the roof area and angle 'to the sun' i.e. is here a south facing side to your house, and can it be made strong enough to support PV?

 

I know that there are parts of Aylesbury that still have very poor water pressure and flow, so get your water pressures and flows checked out.

[Zoo]

@Nickfromwales and @SteamyTea this is all remarkably helpful. A lot of homework you've set me. thank you.