UFH in a Passive House

[Alex C]

I have a passive spec house with a tiled ground floor slab. I would say definately have ufh having lived in the house through the winter. It is not that you couldn't heat the house with another heat source, but that it is not comfortable walking round the house without shoes on with a cold unheated slab. I found that with the slab at 20 degrees or cooler the floor felt quite cold to the touch, whereas if it is only a couple of degrees warmer it is fine to walk on bare foot. I found it only took having a heat input once or twice a week over the winter for a few hours to keep the slab topped up to a comfortable level. Our slab is slightly thicker than most at 200mm and with ufh about 100mm down. This was due to the amount of steel but seems to even out temperature fluctuations really well. If you heat the air rather than slab you may also find it dries it out and may well be unpleasant to live with. With the cold dry snap of the beast from the east our relative humidity in the house dropped to 35% and normally runs at about 45%. We put electric ufh in bathrooms and used it all winter for an hour a day, the tiles felt cold to the touch without it. Also have wet heated towel rads in bathrooms which I ran for an hour a day over winter to boost the upstairs temp. We have no other heating upstairs but this worked really well.

[Gone West]

7 hours ago, Nickfromwales said:

 

I'd be interested to hear, possibly from @PeterStarck

Okay, I don't know how scientific this is, but my house has a space heating requirement of 13kWh/m2/a and a heating load of 9W/m2. There is currently no heating of any kind in the house. The outside temperature was 22.8C and it was sunny when I took the temperatures. The wetroom on the ground floor has porcelain tiles directly onto 200mm concrete which has 300mm EPS underneath. Air temp. 24.1C, floor temp 22.6C, room in shade, I've had showers in there and haven't found the floor cold. The hall on the ground floor has the same makeup as the wetroom. Air temp. 25.4C, floor temp 24.1C, some sun. Bathroom on first floor has Amtico Spacia vinyl tiles on 32mm timber flooring with insulation underneath. Air temp. 25.4C, floor temp. 25.3C, some sun. Bedroom on first floor has 14mm bamboo flooring on 2mm underlay on 22mm timber flooring. Air temp. 25.3C, floor temp 24.9C, room in shade. Wendy likes the house warm, which some people would find hot. I don't mind at all, probably old age. The thermostat in the old bungalow was set at 24C, which is why we got through so much oil. I don't bother monitoring temperatures, Wendy is the best judge of comfort levels.

Edited April 19, 2018 by PeterStarck

[Gone West]

6 hours ago, hejdavies said:

 

Thanks Peter... and is it fair to say that the electric towel rails suffice in the bathrooms - ie the floor is perfectly comfortable to walk on bare foot in the morning in winter..??

I think the solution is in the flooring material. In the bathroom and ensuite we have vinyl floor tiles and they are fine. It really shouldn't make any difference whether it's summer or winter because in a PH the temperature doesn't vary much.

[jack]

1 hour ago, PeterStarck said:

Wendy likes the house warm, which some people would find hot. 

 

Wow, I would literally - LITERALLY! - melt living in your house. 20-21 degrees in winter is more than pleasant for me.

 

When the air temp gets above 23 degrees in the house, I start suffering. Apparently spending a lot of time in Australia in the past did nothing for my heat-tolerance!

 

Like Jeremy, you clearly have a lot more solar gain than us. 

[vivienz]

54 minutes ago, jack said:

 

Wow, I would literally - LITERALLY! - melt living in your house. 20-21 degrees in winter is more than pleasant for me.

 

When the air temp gets above 23 degrees in the house, I start suffering. Apparently spending a lot of time in Australia in the past did nothing for my heat-tolerance!

 

Like Jeremy, you clearly have a lot more solar gain than us. 

I suspect there is an element of the male/female concept of what is comfortable ambient temperature going on here. 20 to 21 degrees indoors is still light jumper temperature for me, although draughts have a lot to do with making it feel cooler.

[jack]

40 minutes ago, vivienz said:

I suspect there is an element of the male/female concept of what is comfortable ambient temperature going on here. 20 to 21 degrees indoors is still light jumper temperature for me, although draughts have a lot to do with making it feel cooler.

 

Absolutely. My wife will use a duvet all the way through summer. I'm too hot under one even in the middle of winter. It's the same for most couples I know.

 

There's also an element of me being cheap (plus wanting to use less energy in principle), so I'm happy to put on warm clothing if it's cold, rather than just turning the heating up.

[Gone West]

@Nickfromwales So was my data of any use in helping you decide whether UFH is worth the bother in a PH?

[Onoff]

14 hours ago, jack said:

Like Jeremy, you clearly have a lot more solar gain than us. 

 

Nothing to do then with 350mm 'ish of icynene & his air tightness results being off the chart?

[Nickfromwales]

36 minutes ago, PeterStarck said:

@Nickfromwales So was my data of any use in helping you decide whether UFH is worth the bother in a PH?

Bugger....he's chasing me for that pint 

[Gone West]

I'm not holding my breath .

[ragg987]

I once came across an article on the 'net that tried to establish how comfortable people feel when they step on a cold floor, with one variable being the material they stepped on. I cannot find it right now and do not recall the details, but the conclusions were along the lines of:

• if the floor is cold people tend to feel less comfortable even if the room is warm
• floor being cold is not just based on floor temperature but depends on the material
• e.g. stone floors feel colder than wooden floors at the same temperature

We all know this instinctively / through experience, but it still surprises me how many people have hard tile or stone floors in their bathrooms which feel cold and echoey despite having heating. Much as I love stone floors, this is a no-no in my view, unless you live in a much warmer country or keep the floor warm through UFH.

 

Based on this we went with "softer" surfaces upstairs where we have no UFH - i.e. Amtico and timber. Amtico has a slight give that also aids comfort and reduces noise. Our bathrooms only have a diect electrical heated towel rail for heating, and stepping on the Amtico feels comfortable. I tend to leave the towel-rail on 24x7 in winter at the lowest setting - perhaps about 50W on average.

[jack]

1 hour ago, Onoff said:

Nothing to do then with 350mm 'ish of icynene & his air tightness results being off the chart?

 

Hey, our insulation and airtightness are alright! Well, some of my windows are due a bit of a adjustment after a couple of years... 

 

It's mostly a combination of low solar gain overall (mostly due to trees) and large windows in places where they're net losers due to orientation.

 

As a guide, we went away for three weeks from mid December, and turned *everything* in the house off. I estimated that the house was 13^oC when we got back, which I didn't think was bad given nearly zero heat input for three weeks other than limited solar gain.

 

Anyone care to estimate what temperature a house built to building regs standard (or worse) would have been at in similar circumstances?

[Onoff]

Warm = Comfort?

 

I've a single, straight length, 22mm plastic, temporary CH pipe laid just sub surface in the stairs room adjacent to "the" bathroom. I had to re-route the old single pipe system to sort the bathroom way back. It's literally laid in a channel and barely filled with a weak cement mix. It has carpet tiles on top. (One day the whole floor is coming up).

 

Annoying friends and family who "come to see how the bathroom's doing" always seem to find the warm spot and joke that I've at least finished the UFH. I'm sure if we still had the cat it'd be stretched full length. No other source of heat in that room and tbh it does feel lovely to stand on!

 

I never did find what the iron pipe crossing it by the door is...

 

 

[TerryE]

Have a look at my blog. We put UFH in our slab during the pour so it cost very little, less than £2K. We use a Willis heater as our heating source, and I did the work myself. We use 2 x SunAmps for DHW, and our cooking is electric (though we do have 2 Propane gas rings on our hob as backup). So excluding the SAs, the cost of the installation including the cost of control system was around £1K. 

 

Because of planning constraints, we only have limited glass, and this has upsides as well as down. We stopped adding heat about a week ago, but the arrival of spring temperatures was unusually late this year.

 

Have a look at 

 

At the moment our daily energy costs are ~£2, (but no PV; thanks to the planners).

 

And we are absolutely delighted with how the system works. 

Edited April 20, 2018 by TerryE

[Nickfromwales]

On 20/04/2018 at 08:01, PeterStarck said:

@Nickfromwales So was my data of any use in helping you decide whether UFH is worth the bother in a PH?

Yup, it was. All jokes aside your feedback is most definitely of value as you have a reasonably unique heating arrangement compared to most on here. Not many have been brave enough to reply on predictions to the point that they didn't fit UFH, anywhere, on purpose.  

Does the 185 provide space heating as it arrived out of the box, or does it have a pre / post duct heater unit as a bolt-on? Just curious how you get your temp up to 24 and how you achieve such a small differential between the floors and the air space. As im currently specifying this exact same beast for someone, I just wondered how an air temp of 21-22oC would affect the floor temp. 

Can I ask if you have a concrete slab or floating floor over insulation ?

Each answer takes you one step closer to that succulent, ice-cold pint 

[Gone West]

@Nickfromwales It has a built in EASHP rated at 585W which provides hot water and warm air heating. The hot water has priority and the EASHP will heat it to a max. of 55C. There is a 1kW 'immersion heater' which is just a coil in a pocket in the side of the tank which will heat it up to 65C. The warm air heating is up to around 45C. It works straight out of the box and all these settings can be adjusted on the control unit. We have a porcelain tile on 200mm concrete ground floor and bamboo flooring on 22mm chipboard first floor. The model we have is the LS which has the larger compressor. I think it only works because it's a small house and has a very low space heating requirement. The smaller S model would struggle unless in a small, very well insulated flat. Our main heating is supplied by the three electric towel rails in the bathrooms and around 4m2 electric UFH in the kitchen.

I prefer my pint of Glenfiddich at room temperature.

[oranjeboom]

1 hour ago, PeterStarck said:

I prefer my pint of Glenfiddich at room temperature.

 

18C or Wendy's 24C? Bet you have to drink it fast before it evaporates!

[Nickfromwales]

8 minutes ago, PeterStarck said:

Our main heating is supplied by the three electric towel rails in the bathrooms and around 4m2 electric UFH in the kitchen.

Ok, so when you say main heating, do you mean adventitious heating that goes towards reinforcing the performance of the 185? Do the towel rads and (E)UFH have to be on to maintain the overall ambient temps? 

For a larger house, I wonder if a pre-heater in the intake duct would be required. Space heating can be supplemented by the second HE in the SA ( dual port ) unit eg transferring heat energy from PV >  SA > airflow via a wet circuit. 

 

12 minutes ago, PeterStarck said:

There is a 1kW 'immersion heater' which is just a coil in a pocket in the side of the tank which will heat it up to 65C.

I assume for legionella purge? Can that be timed to coincide with midday ( peak ) PV output? Thoughts were that I may set this up to accept pre-heated water from a SA, so PV provides the majority of DHW ( in a larger house than yours btw ). 

 

1 hour ago, PeterStarck said:

We have a porcelain tile on 200mm concrete ground floor and bamboo flooring on 22mm chipboard first floor.

I think this helps, as it gives some thermal retention / stability ( or other suitably phrased what-not ). For an engineered wood over a floating chipboard floor ( over a passive spec B&B floor ) im not so sure the underfoot experience would be so acceptable

[Nickfromwales]

1 hour ago, PeterStarck said:

I prefer my pint of Glenfiddich at room temperature.

Holy ?

[Gone West]

6 hours ago, Nickfromwales said:

Ok, so when you say main heating, do you mean adventitious heating that goes towards reinforcing the performance of the 185? Do the towel rads and (E)UFH have to be on to maintain the overall ambient temps? 

It's not adventitious because when we designed the house we wanted the bathrooms to be a little bit warmer than the other rooms. The advantage of that is that the air extracted from those rooms can help warm the incoming air to the house. The towel rails are always on,unless those rooms are warm enough without them.

 

6 hours ago, Nickfromwales said:

For a larger house, I wonder if a pre-heater in the intake duct would be required. Space heating can be supplemented by the second HE in the SA ( dual port ) unit eg transferring heat energy from PV >  SA > airflow via a wet circuit. 

I don't know how effective a pre-heater would be, I guess it would depend on where in the country you live.

 

6 hours ago, Nickfromwales said:

I assume for legionella purge? Can that be timed to coincide with midday ( peak ) PV output? Thoughts were that I may set this up to accept pre-heated water from a SA, so PV provides the majority of DHW ( in a larger house than yours btw ).  

Yes, I've never used it. We have the hot water set at 45C. I think it can be timed to come on whenever you want. It sound feasible.

 

6 hours ago, Nickfromwales said:

I think this helps, as it gives some thermal retention / stability ( or other suitably phrased what-not ). For an engineered wood over a floating chipboard floor ( over a passive spec B&B floor ) im not so sure the underfoot experience would be so acceptable

I'm sure if the surface of the flooring is insulating it will be as comfortable underfoot as a heated less insulating surface.

 

6 hours ago, Nickfromwales said:

Holy ?

On the rocks is swearing.

[Nickfromwales]

3 minutes ago, PeterStarck said:

Yes, I've never used it. We have the hot water set at 45C. I think it can be timed to come on whenever you want. It sound feasible.

One would assume the 185 will purge this once a week as 45oC is a little close to the wind for staving off the heebeejeebees. 

[CalvinHobbes]

On 18/04/2018 at 15:42, joe90 said:

Even in a passive house a small amount of heat is required and UFH is a more comfortable way to heat, requires lower water temps ( so ideal for ASHP), I have UFH on the ground floor ( as one zone) and no heating upstairs apart from towel rads in the bathrooms and electric UFH in our en suite. My theory ( as we are yet to move in and try it out?) is that if upstairs gets a little cold in the middle of winter a couple of portable electric heaters are more than suffice.

 

cross posted with Peter, yes I have installed a separate pump on the UFH manifold so I can shift heat about without firing up the ASHP. we are facing south so should get solar gain.

How did that go? Our architect planned in radiators upstairs but where we live now which isn't passive we never have the heat on upstairs. I am thinking we could do like you and lose the radiators upstairs just keeping the ashp downstairs. 

[joe90]

6 hours ago, CalvinHobbes said:

How did that go?

Very well, I know others here have put radiators in upstairs but never use them but future buyers might be frightened off by not having them. 

[TerryE]

2 hours ago, joe90 said:

future buyers might be frightened off by not having them

 

I am not sure that you can 2nd guess future buyers potential thoughts, especially if you have no plans to sell your house.  In our case we have no rads, no gas, no ASHP; just one 2.88 kW Willis -- plus 6+ years of logged temperature data and daily electricity use and costs.  Our current electricity bill thanks to the Agile Tariff and spot electricity prices is the lowest it's ever been.

 

Edited April 30 by TerryE

[joe90]

59 minutes ago, TerryE said:

I am not sure that you can 2nd guess future buyers potential thoughts,

Oh I agree which is why I didn’t but if I remember correctly at least one person here did that. Most buyers don’t even take notice of the EPC but with escalating energy costs and better building regs I believe in the future “cost of running” will be factor when buying more than it is now.