Heating the house scenario.

[Russell griffiths]

So a situation is happening in our old house, which isn’t a problem as we have a wood burner that heats the house up nice and quick but what about the new place. 

 

New house, nicely insulated, good windows, underfloor heating. 

 

Now the scenario that has happened lately. 

Lovely spring days, 15-16 degrees outside, the underfloor heating is off, the patio door is open, back door open and dogs running in and out, and a nice breeze is keeping everything feeling comfortable. 

At 6 in the evening it starts to get a bit chilly so we pull the patio door up, back door still open, dogs still rampaging about, it gets a bit colder so the dogs come in for dinner and the back door is pulled shut. 

How do we now lift the temperature in the house up, it has dropped to 8-10 degrees outside. 

Will it take to long for the ufh to have effect?

will the oven on and the dogs farting away in the boot room be enough, do I light a load of candles, 

 

its as though we need a big blast of instant heat, fake gas fire?  Wood burner? Hairdryer?

 

any thoughts people. 

 

[Jeremy Harris]

You'll find that the new house, with much better insulation and airtightness, just won't lose heat. 

 

Take ours as an example.  Yesterday it reached about 23°C outside, and the house sat at about 22°C.  We had the French doors open to the garden for half the day.  Come the evening it cooled down outside, but we just shut the doors and the house was still at about 22°C.  We had no heating or cooling on last night, and this morning I came down and the house was at 21.9°C and outside it was 12°C. 

 

 

[ProDave]

It is amazing how a well insulated house keeps it's heat.  The overriding thing I find with our house it it takes a long time to cool down.  It also takes a long tiome to heat up as the UFH runs at a low level, but that is not a problem.

 

Interesting how much the climate varies across the UK. yesterday was 11 degrees, grey and drizzling. The house was at 21 degrees but there is something about when it is grey and damp it "feels" cold so we light the stove last night.  Today is only 9 degrees and still grey and wet, I think the stove will be used later, again the thermometer says it is not cold, but......

[Ed Davies]

2 hours ago, Russell griffiths said:

its as though we need a big blast of instant heat

 

Assuming a thick slab, would the slab have cooled much even if the air in the house had dropped quite a few degrees? Obviously if you've had the doors open in cool weather for a few days the slab will have cooled down but then you'd expect a long warm up but if the slab's still close to the right temperature surely the warm up will be pretty quick.

[joe90]

Ours is a heavy house and stays very stable, I do however tend to close the bifolds (to kitchen and lounge) before the temp drops too much outside to retain the heat we have gained. Yes with UFH there is no “instant heat” when the skin becomes a little chilly of an evening. This is one reason we have a wood burning stove, caveman feeling when it “looks” cold outside.

[Russell griffiths]

1 hour ago, Ed Davies said:

 

Assuming a thick slab, would the slab have cooled much even if the air in the house had dropped quite a few degrees? Obviously if you've had the doors open in cool weather for a few days the slab will have cooled down but then you'd expect a long warm up but if the slab's still close to the right temperature surely the warm up will be pretty quick.

 

Assume the ufh has been off for the last week so floor has cooled. 

 

We think spring is here, all heating off, but at 6 pm cold chill descends, it’s at this point we need a blast off hot to get it all toasty again. 

[Jeremy Harris]

Just now, Russell griffiths said:

 

Assume the ufh has been off for the last week so floor has cooled. 

 

We think spring is here, all heating off, but at 6 pm cold chill descends, it’s at this point we need a blast off hot to get it all toasty again. 

 

 

The floor won't have cooled, though.  That's the big advantage of having a well-insulated slab, it will sit at close to the room temperature and take ages to cool down, and then will only cool down when the house is colder then the slab for a long period of time.

 

@Ed Davies's description above is exactly what happens, and in our case this contrasts sharply with our old house, where the slab was only slightly above ground temperature all year around, as it had no insulation underneath it.  At the old house, during the evening after a warm day, the slab wouldn't heat the house, as it was too cold to do so (might be at around 10°C or so).  In the new house the slab will be around the same temperature as the rooms during the day, so when you need a bit of heat in the evening the slab provides it, without needing to be topped up by the UFH.  In practice the slab sits at around the mean house temperature, so will warm up a bit during hot days, then give back heat to the house and cool down very slightly on cooler days.

[ProDave]

8 minutes ago, Russell griffiths said:

 

Assume the ufh has been off for the last week so floor has cooled. 

 

We think spring is here, all heating off, but at 6 pm cold chill descends, it’s at this point we need a blast off hot to get it all toasty again. 

That's the point we are making.  The house won't cool that quick.

 

It's been pretty cool for a couple of weeks here and the house is still keeping at 21 degrees with an outside temperature in the order of 11 degrees and no heating on.  We only light the stove last night for effect, not because it was really cold.

[lizzie]

Sliders open pretty much all day, most days this last week..... woofer likes it that way...... house temp pretty steady at about 22 day and night, ufh not kicked in for over a week.

[Nickfromwales]

6 hours ago, Russell griffiths said:

 

Assume the ufh has been off for the last week so floor has cooled. 

 

We think spring is here, all heating off, but at 6 pm cold chill descends, it’s at this point we need a blast off hot to get it all toasty again. 

It's really quite difficult to comprehend in fairness. It's just never cold. The fabric of the build, walls / floors / fittings etc retain the heat from the day and the whole house 'interior' acts as an emitter. In the current build we're on, over Xmas and with the UFH flow temp on at a little over 22^oC, the house maintained 18-20^oC dependant on the amount of solar gain during the day. That was without a working MVHR system, with 2x 180mm holes ducting out through the roof, and a leaky ( unfinished ) airtight door to the garage.

We would open all the large sliders, the double garage door, the utility door to the garage, and the front door to let the ( bloody cold ) air whistle through whilst the floors were swept up and the dust was intolerable. That saw the inside air temp drop to around 7^oC for the duration of the cleanup. Upon closing all of the openings, the temp of the house would stabilise within minutes back to the previous comfortable 20.5^oC it was to start with. You just cannot suck the heat out in such a short space of time. If youve had a good enough day to have the doors all open and the 4-legged walking fart-boxes running through, then you'll have had heat input into the house fabric whether you wanted it or not. The secret is the fabric's ability to retain it.

Turning the UFH off on a Monday would see a notable drop by around Wednesday. No sooner. That's WITHOUT heat recovery remember  

 

I really do wonder when our dogshit British building regs will get a swift kick in the nether region.............Don't hold your breath.