Lowest outside temperature without heating

robert32

Hi there,


Please can someone advise what is the lowest outside temperature it is possible to leave a house unheated at?


I recognise there are differentials for each house depending on quality of insulation, drafts, etc.


I have read that temperatures can drop to -5°C outside before water in inside pipes starts to freeze.






Thanks,


Rob.

Ebe_Scrooge

Impossible to say. For instance, if the house is well-insulated, and you've had the heating on all day, the fabric of the house will have absorbed quite a lot of heat. Switch off the heating overnight, outside drops to -15, heating comes back on in the morning - no problem at all, the interior will not have dropped to anything like freezing point.


Conversely, leave the house with no heating for a month, it'll end up being exactly the same temperature as outside, so zero degrees would be enough to freeze the pipes.


Most modern systems have a frost-stat for just this scenario - if you're going away for a few days, you can leave the heating off, but if the temperature drops too low ( it's usually set to something like 5 degrees ) the frost-stat will kick in and fire up the boiler, just enough to stop things freezing.

footyguy

-273 degrees C

Don't believe all you read on t'internet.
Refer to the laws of thermodynamics for your answer
(Pure) Water freezes at 0 degrees C

Ebe_Scrooge

footyguy wrote: »

-273 degrees C

Minus 273.15 degrees C, surely ?:)

robert32

It's not the most well-insulated house, but is a semi-detached. It's had the heating off for a couple of weeks. How would it cope in a 7-hour period of temperatures at 0 and just below?

Ebe_Scrooge

It depends.


You'd probably be OK, especially as you'll be getting a bit of heat transfer from next door ( assuming they've got their heating on ). But to save any expensive disasters, it's safest to either make sure you've got a functioning frost-stat in the system, or else leave the heating on very low. It doesn't need to be on constantly - maybe set it to come on for a couple of hours at say midnight or 2 in the morning, when the outside temperature is likely to be lowest. And really, if you've only got the heating set really low ( say 8 or 10 degrees ), the amount it's going to cost you is negligible compared to the consequences of having your pipes freezing.

matelodave

Have you got pipes or tanks in the loft or possibly under the floorboards. These places will get a lot colder quicker than the rest of the house as they are outside the heated area so although the heating system may be OK the stuff in the loft relies on heat rising from the house - that's why you should never insulate underthe water tanks.

As said above a day or so should be OK because there will be residual heat in the house. Hoever the internal temperature will get get down to the same as it is outside after a few days of freezing, foggy weather. A bit of sun on the house will help warm it a bit but you wont get any benefit from the sun, if it's cloudy, foggy or the place is covered in snow. Wind will accelerate the cooling as well.

Interestingly the coldest time of the day is around dawn rather than around midnight.

You really need to set a frost protection temperature of around 5 degrees if you want to avoid an expensive leak.

I can assure you that the disruption, redecorating and aggro will cost you a lot more than having the heating on low, even if you are insured.

If the place is totally unoccupied then consider draining it all down. There's still another 6 weeks or so of potetially cold freezing weather - maybe more depending where your house is situated

Swipe

It would take a prolonged cold spell 3+ days of sub zero temps (-5C or below) for internal pipes in a house with no heating to freeze.

Gloomendoom

We have left our house empty for a month in the winter several times. The central heating is controlled by a Hive which will turn on the heating if the inside temperature drops to 7°C. So far, it has never done this. Outside temperatures have dropped to -7°C at times, although not for a prolonged period.

The house is stone, single glazed and, apart from the roof, uninsulated.


I think that there are too many variables to give specific advice though..

Cardew

I have a detached annex(converted stables) to my house with gas CH. It is not cavity wall insulated(but dry lined) and not double glazed.

I set the frost stat to 5C and as it is unoccupied most of the time. The amount of gas it uses over a whole winter is minimal. So to my mind it is not worth taking a chance by leaving heating off.

G_M

footyguy wrote: »

-273 degrees C

Don't believe all you read on t'internet.
Refer to the laws of thermodynamics for your answer
(Pure) Water freezes at 0 degrees C

Errrr.... if you're going to get scientific, hadn't you better mention the height above ground level...?