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I am a new member at the planning stage of a new build house for our retirement and looking to make it as comfortable, efficient and maintenance free as possible. I am trying to get my head round the many and various heating options – things have changed beyond recognition since we built our current house 35 years ago.

The plan is that we will have one large room incorporating living/kitchen/dining. This will be on the first floor with ceiling at roof height and extensive glass to S & W to maximise the views. I know this isn't ideal, but we love the outdoors and the views are spectacular. Bedrooms all ground floor. My current thinking is to have wet UFH in concrete screed floors on both levels; either GSHP or ASHP (current preference).  Can the ASHP be located in an outbuilding to avoid noise issues?

My main concern is solar gain:-

Can I utilise this free energy to heat the lower floors/DHW in winter (MVHR)??

How do I keep it cool as we experience the ever warm summers we are promised? (MVHR/AC/??)

Thanks in advance

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The ASHP would be located outdoors and are really quiet so noise should not be an issue. We have a south facing sunspace (conservatory) which we have been told will over heat but we have solar glass to cut this somewhat and when it’s warm out there we open bifolds into the kitchen diner and lounge and the heat warms the house quite nicely. As you will see from numerous threads on here MVHR are very poor at moving heat via air (although I know of one that does). To negate solar gain you may need shades of some sort outside the glass on those warm days. We like the outdoors and views hence our South facing sunspace and on cooler winter days a nice place to sit in the sun but out of the cold.

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Posted (edited)

We've already started some of this feedback on your other thread, so I won't repeat myself here.

 

2 hours ago, SlivenClod said:

extensive glass to S & W to maximise the views. I know this isn't ideal

 

Correct, large areas of S & W glass will give to U-value losses in the winter and large solar gains Spring - Autumn.  You will really need to include your cooling solution for these rooms if you aren't going to cook.   As @joe90 suggests having a separate environmental zone external to the main fabric of the house such as a conservatory or atrium might  the best of both worlds. 

 

If you get the spec of the house correct then you will only need the equivalent of an average 1-2 kW heat input during the winter and UFH on the ground floor is more than enough to provide this.

 

Yes IMO, solar gain can be a net benefit during winter, but localised overheating in the other three months is a pain in the a**e to control.

Edited by TerryE
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As I type this, at nearly 6pm, our house has had the cooling on for around 3 hours, due to bright sunshine this afternoon (the cooling is managing to hold the room temperature down to around 23.5°C, we tend to prefer the room temperature to be around 22°C).  We don't have a massive amount of glass, but it's more than enough to allow the house to get uncomfortably warm without active cooling.   Our heating hasn't been on at all for the past couple of weeks or so, either.

 

It's largely a problem in spring and autumn for us, when the low sun angle allows the sun to penetrate more deeply into the house, but it's still a PITA to deal with.  I dearly wish I'd been able to fit external blinds or shutters, and may well try to see how receptive the local planners would be to me adding them now (they weren't happy with the idea of shutter originally).

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You are thinking about the fundamental questions in the right areas here.

 

My comemnts:

 

Assuming you are going for a well insulated house.

 

1 - Take time to think it through *very* carefully, and visit people who are already in that situation.

2 - The heat from solar in winter is very little compared to summer ... perhaps only 10%, so there will be a potential benefit but it will not be huge.

3 - You need to be thinking about significantly large overhangs (think 2m downstairs or perhaps 3m+ if it is at double height (or you could go for 2 layers with a balcony upstairs). The aim is to keep out the high sun in summer, and let in the low sun in winter. BUT as you would guess ... the difficult case that needs care is the sun in spring and autumn, where there is lowish sun with highish heat.

 

Consider how you can incorporate such overhangs in your design and natural usage for your house, and whether you want to use things that are structurally based off the ground, attached to your houise,or separate (eg pergolas), and consider if you need to design anything in such as powered blinds or solar glass (*),

 

Ferdinand

 

* Of course if you keep all the autumn excess heat out with glass itself you are then buggered for the winter benefit :-). The important thing is to take more time to think than you expect to need.

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Posted (edited)

@SlivenClod, I recommend you model the thermal characteristics of your house using PHPP. You can do it yourself if you are skilled with spreadsheets and willing to put in some time, or you can hire somebody to help. Either way, the relatively modest cost (in time or money) has the potential to pay-off handsomely in comfort once you have built your home and are living in it.

 

Over heating is not to be underestimated in a well insulated home. We have seen some people here on BuildHub needing much work to control it after finishing their homes.

 

It is always better to prevent overheating in the first place (as mentioned above) than to deal with after it has occurred.

Edited by Dreadnaught

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Posted (edited)

One of the things that modelling cannot get exactly right (I believe) is local topography, we are in a flat location near the Atlantic and (in my opinion) get a lot of windwash that can suck the heat from the outer skin unless there is no wind (rare). @JSHarris is in a hollow and a suntrap which may be why his overheating at times is not quite what the calculations showed. We are yet to have a summer with our south facing conservatory so we are yet to see how it performs but so far (spring) it’s been great.

 

edit to add, I did no modelling at all, just gut reaction on what I felt was right and followed passive house principles. Let’s hope I was right 🤔

Edited by joe90
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