How to heat my Huse

renex

Cardew wrote: »

So 3,200 square feet for the ground floor.


How many floors?


You are having a mansion built, with an architect designing it, and you are asking the most basic of questions, on an internet forum.


Mmmmm

it is 2 floors and, my financial situation allows me to build such a grand house. i am reluctant to go into details for security purposes. also i have a lot of time on my hands at the moment so i figured why not attempt to learn some of the options for myself. after all knowledge is power.

Smiley_Dan

I agree. You have a lot to learn. Do not settle for building regulations, remember they are worst-allowable practice, not best practice.

Silent_Dancer

Given the size of the house and the swimming pool you are going to need a commercial heating system. I suggest speaking to someone who is used to designing such systems.

reeac

I'm always intrigued by statements on TV programmes etc about people who have such well insulated houses that they have zero fuel bills. Our bungalow is of conventional 1997 building regs. Spec. Ie. Insulation block inner walls, filled cavities, underfloor insulation, full sealed double glazing, 150 mm. Roof insulation etc and yet we use ca 1800 to 2000 litres of oil per annum ie. 18,000 to 20,000kWh per annum. Do these other people wear loads of sweaters and only bathe once a week?

Smiley_Dan

reeac wrote: »

I'm always intrigued by statements on TV programmes etc about people who have such well insulated houses that they have zero fuel bills. Our bungalow is of conventional 1997 building regs. Spec. Ie. Insulation block inner walls, filled cavities, underfloor insulation, full sealed double glazing, 150 mm. Roof insulation etc and yet we use ca 1800 to 2000 litres of oil per annum ie. 18,000 to 20,000kWh per annum. Do these other people wear loads of sweaters and only bathe once a week?

Well it's because building regs are nowhere near adequate to achieve high levels of energy efficiency. Building regs are a worst permissible target, certainly not best practice!

In your case you have nowhere near enough loft insulation, no idea what your windows are like but they vary massively, and your walls depend on how much insulation is installed and crucially how well it has been installed.

The big elephant in the room is air tightness and building regs are especially lax in this regard. For many houses built in the 80s (not necessarily yours) and since this can be very poor because of practices like dot and dab plasterboard.

Zero fuel bills are certainly achievable without sweaters and are houses which are far more comfortable and healthy to live in than alternatives.

reeac

So let's say that my current energy input is 19,000kWh pa from oil plus 3500 kWh pa from electricity (used for cooking, lighting etc not specifically for heating) i.e. 22,500 kWh pa total. If I could somehow cut my current U values to one third (!) then that would bring it down to 7,500 which would be 3,500 electricity plus 4,000 oil or 400 litres pa.....still not zero. Re. air change losses I considered installing a heat exchange ventilation system when our place was built but my calculations showed that the heat savings were very small. Our front and back doors both feature air lock style lobbies. We also have main rooms facing South with plenty of glazing there. Re roof insulation, yes I'm aware that 300 mm is better than 150 mm. but the reduction in U value is quite small. With all U values diminishing returns apply as you pile on the insulation.

Smiley_Dan

It wouldn't be as simple as simply lowering U to reduce the demand. It would help but needs to be done in conjunction with reducing air permeability (aka making the house more airtight).

The 'trouble' with this stuff is that there's diminishing returns, which might be what you found with the MVHR. However once you get to that level almost all the heat loss is via air infiltration, and so to go to the next level you have to get very air tight and that means you will need a ventilation system (MVHR preferably).

That said, that's the physics, you can't change it. You just have to purchase more insulation and get more air tight. This is why it's best to do it at build time - it just gets done altogether and doesn't cost a great deal extra. For the air tightness, it is also hard to do retrospectively because of all the dodgy building practices I mention above.

It's also worth mentioning there are companies that will assess your house in a more holistic and exhaustive manner than an EPC - there are a lot of these but look at the "advisors" on the SuperHomes website: http://www.superhomes.org.uk/get-informed/my-green-builder/

Oakgreen

Hi - Regarding radiator sizing Cardew is right to suggest the lower flow temperatures, and that radiator size is related to the room losses, your architect or heating engineer should have worked these out, just make sure they have not assumed a conventional boiler is being used.

My radiators were sized for 45c at the design outdoor temperature of -3c, my system is a gas boiler and heat pump hybrid and the design allowed for the gas boilers higher temperature when it got cold outside, the radiators which needed to be replaced did not work out much larger i.e. swapping single panel for double panel in most cases, maybe a hybrid heat pump/oil system would work for you?

in reality the system very rarely decides to run the gas boiler (based on cost) and the heat pump manages to do the job even in cold weather when at 45c the radiators are in theory undersized, guess the calculations were not 100% true to real life - overall the system does the job required very well