Do we need a Gas connection?

[EquiumDuo]

Hi All,

So we are getting into the gritty detailed design phase for our future house and I feel like I am coming up against some strong opposition for my ideas for heating/cooling/Hot water for the house.

 

Briefly:

Outer Concrete Block

50mm Airgap

50mm PIR in Cavity

Timber Frame 140mm studs, Filled with PIR insulation)

OSB outer with likely Tyvek HouseWrap

Inner Dupont AirGuard

30mm service cavity.

Plasterboard.

The roof will be a warm roof, Again >200mm insulation (PIR)

The windows and doors will be a high spec double glazing.

Basment will have 100mm of polystyrene on the outside, plus some internal insulation.

 

Basically a hemetically sealed well insulated rectangle. Nothing particularly special about what we are doing.

 

With regards to heating, based on everything I have read, the blog posts etc. We are in a south facing plot (with about 20sqm of frontal glazing) and due to the sloping plot very well protected from the wind. I don't think a gas boiler is going to be needed. (We are in a gass supply area).

 

We will have UFH on the mainfloor + the esnuites/bathrooms. We will have MVHR. I would very much like to go for an Air Source heating solution with large unvented cylinders for hot water storage. Based on everything I have read, all the youtube videos and all the other reading materials. I think we will need to cool the building more than heat it. We will plan to run the "heating" 24/7. Maintain a very consistent temperature throughout the day, with maybe a little variance overnight, but probably not.

 

A gas boiler doesnt seem to fit this usage. I would describe it as a "Bang Bang" heating system. Not offering the relative granular control of what an air source could provide based on the actual amount of energy we would need. Would love some input on this. My opposition hasn't really given me a good challenges to my idea apart from "its better to have it than not, you'll regret it, everyone has gas, etc..."

 

Co-incidently if anyone has a heating engineer they could reccomend, I would be appreciative. I've done some calcs myself but I'm just a novice with an excel sheet

[PeterW]

How close is gas to the house ..?? You can always put a buffer tank in and the smallest gas boiler you can find to stop short cycling but you’ll need to manage the heat loads carefully. 
 

If you have any sort of atrium that

could take an air to air heat pump then that will be your best bet for cooling.  

[Temp]

The relatively high cost of electricity vs gas (per kWH) means you need your ASHP to be running at close to maximum COP. This makes correct sizing of the ASHP important. Otherwise go for it.

 

We have oil fired UFH and have it "on" 24/7, however we use set back on the thermostats to reduce temperatures  at night.

[pdf27]

Who is the opposition from and what do they want to achieve? My wife isn't too fussed about how we heat it but really wants active summer cooling. Past that she doesn't really care how it's achieved.

[EquiumDuo]

6 hours ago, PeterW said:

How close is gas to the house ..?? You can always put a buffer tank in and the smallest gas boiler you can find to stop short cycling but you’ll need to manage the heat loads carefully. 
 

If you have any sort of atrium that

could take an air to air heat pump then that will be your best bet for cooling.  

The gas is very close to the house, in the pavement in front of the house. I want air to air heat pump to take advantage of cooling also. I read a blog by one of the guys here (the name is gone from me at the moment). Who used it to cool his UFH system. Great info in his blog.

 

The opposition is my father (who is a builder) and my wife's father (who's not). I've agreed to speak with a heating engineer. So need to wait for the SAP calcs first.

[Bitpipe]

Problem with many  heating trades is they are used to designing systems for poorly insulated houses that are cold in winter - so its rads in every room or UFH in a thin screed on a poorly insulated slab.

 

Few are experienced with low temp systems which is where ASHP tends to do well.

 

 

7 hours ago, EquiumDuo said:

 

Basment will have 100mm of polystyrene on the outside, plus some internal insulation.

 

 

Will your basement slab be insulated underneath? Ours sits on 300mm (overkill, 200mm would have been enough) of EPS 200 grade which the SE signed off. It's rock hard and sits on sand blinded hardcore and once covered with a basic membrane will be ideal to build your slab on. Advantage is that you don't need to screed / insulate the basement on the inside - no point doing it twice. 

 

Would up the external basement insulation to 200mm and forget anything inside. Ours has no heating whatsoever and is perfectly comfortable year round - the ambient heat from all the appliances down there (TVs, fridges and the plant room) are more than enough.

 

Are you having a solid or suspended ground floor over the basement? We went for suspended with UFH in spreader plates - works great with our timber subfloor and resin topcoat (when it ever comes on that is). UFH runs at low temp but as we have a gas boiler no option to cool, which I would love.

 

If you're going to be quite airtight then you'll have MVHR also but view it as a way of effectively ventilating your house with minimal heat loss vs any meaningful heat transference.

 

It may well be that you do not need much if any heating upstairs which is a big leap for many people. We just have towel rads and electric UFH in the ensuite & bathrooms.

 

However we are on mains gas as it was then the most efficient heat generator, the new connection was subsidised and it was a known quantity 5 years ago whereas I felt ASHP was still a bit new for us. We have a veru economical boiler though (Woster Ecostar) and also supplement DHW generation with the in roof PV and a diverter.

 

ASHP would probably have worked as well and the summer cooling is a real bonus. Also consider provision (i.e. ducting and services) for a strategically placed split air con - you can install later if needed.

 

You will find that overheating (not just a summer problem) is probably more of a concern than winter heating.

 

[EquiumDuo]

28 minutes ago, Bitpipe said:

Problem with many  heating trades is they are used to designing systems for poorly insulated houses that are cold in winter - so its rads in every room or UFH in a thin screed on a poorly insulated slab.

 

Few are experienced with low temp systems which is where ASHP tends to do well.

 

 

 

Will your basement slab be insulated underneath? Ours sits on 300mm (overkill, 200mm would have been enough) of EPS 200 grade which the SE signed off. It's rock hard and sits on sand blinded hardcore and once covered with a basic membrane will be ideal to build your slab on. Advantage is that you don't need to screed / insulate the basement on the inside - no point doing it twice. 

 

Would up the external basement insulation to 200mm and forget anything inside. Ours has no heating whatsoever and is perfectly comfortable year round - the ambient heat from all the appliances down there (TVs, fridges and the plant room) are more than enough.

 

Are you having a solid or suspended ground floor over the basement? We went for suspended with UFH in spreader plates - works great with our timber subfloor and resin topcoat (when it ever comes on that is). UFH runs at low temp but as we have a gas boiler no option to cool, which I would love.

 

If you're going to be quite airtight then you'll have MVHR also but view it as a way of effectively ventilating your house with minimal heat loss vs any meaningful heat transference.

 

It may well be that you do not need much if any heating upstairs which is a big leap for many people. We just have towel rads and electric UFH in the ensuite & bathrooms.

 

However we are on mains gas as it was then the most efficient heat generator, the new connection was subsidised and it was a known quantity 5 years ago whereas I felt ASHP was still a bit new for us. We have a veru economical boiler though (Woster Ecostar) and also supplement DHW generation with the in roof PV and a diverter.

 

ASHP would probably have worked as well and the summer cooling is a real bonus. Also consider provision (i.e. ducting and services) for a strategically placed split air con - you can install later if needed.

 

You will find that overheating (not just a summer problem) is probably more of a concern than winter heating.

 

Hi Bitpipe,

Yeah this is all hitting points I feel I am addressing.

 

Basement insulation will be 200mm EPS300 underneath, and 2x 50mm overlapping EPS70 on the sides. I feel very confident that the basement will be absolutely fine, I'm also going to run most of the utilities and water tanks down there, as well as some electronic equipment. Its going to be fine.

 

It will be basically posijoist floor with a floorboard and UFH with heat spreader plates for the main floor/groundfloor, Only UFH in the ensuites upstairs. No other heating upstairs. There will be MVHR and there will be air conditioning. I want the cooling capcity for the summers.

 

I feel like the potential PERCEIVED lack of heat capacity from the ASHP is WAY outclassed by the other benefits. I also plan on having an inline instant water heater for the hot water system to "top up" the hot water temp as needed when the cylinder starts to deplete.

[Bitpipe]

20 minutes ago, EquiumDuo said:

Hi Bitpipe,

Yeah this is all hitting points I feel I am addressing.

 

Basement insulation will be 200mm EPS300 underneath, and 2x 50mm overlapping EPS70 on the sides. I feel very confident that the basement will be absolutely fine, I'm also going to run most of the utilities and water tanks down there, as well as some electronic equipment. Its going to be fine.

 

It will be basically posijoist floor with a floorboard and UFH with heat spreader plates for the main floor/groundfloor, Only UFH in the ensuites upstairs. No other heating upstairs. There will be MVHR and there will be air conditioning. I want the cooling capcity for the summers.

 

I feel like the potential PERCEIVED lack of heat capacity from the ASHP is WAY outclassed by the other benefits. I also plan on having an inline instant water heater for the hot water system to "top up" the hot water temp as needed when the cylinder starts to deplete.

Sounds good - would still advise thicker EPS on basement walls as it can get compressed in places when backfilling and the extra

cost of 100mm eps is marginal, plus you can’t retro for

 

Also consider electric ufh for the bathrooms as you’ll use that year round to warm tiles vs the wet ufh running just for the bathrooms. 

[EquiumDuo]

Not a abd idea for the bathrooms.

 

One of my funky ideas is putting some electric UFH matts underneath the stairs outside. It does get frosty in the winter. Having the ability to turn on an electric defrost on the external stairs might be a nice touch. Worth the electric cost to ensure a safe way up to the front door.

[Conor]

100mm EPS isn't nearly enough. We have 150mm in our basement plus an extra 50mm PIR. It's only about £20 for a 2.88m² sheet of 100mm EPS 70 silver. Would only take a day or two to stick it on to the entire basement with expanding foam adhesive.