Minimum effective heating to avoid pipe freeze?

[BookLoverL]

Hi everyone,

Well, I made a possibly-not-very-ERE decision to move into a rental place in my area. But I'm satisfied because living with my parents was driving me up the wall, so I decided I had to change something.

Anyway, obviously now I am in control of my own heating, sort of. I personally am fine to layer up down to pretty low temperatures, but of course if you go too low, the pipes might freeze, and the UK is also pretty humid generally so I'm a little worried about condensation/potential for mould.

The house is a 2-up-2-down mid-terrace with single-glazed windows still. (The literal smallest type of house I could find in the area I actually want to live in. No flats available here.) The heater is a gas-powered boiler, which then powers radiators throughout the house. There's no thermostat, there's just a timer that you manually set. The smallest interval you can have the heater on for is 15 minutes. I can't change the boiler type or the windows, as it's a rental.

Right now I have it set to come on for an hour at 6:30 in the morning and an hour at 7 in the evening. I used my alarm clock, which tells me the temperature for some reason (though I'm not sure how accurate), to measure the temperature at different times in different places. The temperature outside has been typical winter temperatures for here.

When the heating has been on, the cooler rooms of the house get up to around 16C (60ish F). At the point when the heating has been off all day, the larger upstairs room is at around 12C (53.6F), the cupboard under the sink is around 10C (50F), and the very coldest point of the house, the little cupboard at the front where the gas supply comes in and where the water stop tap is, is at around 9.5C (49ish F).

I haven't noticed any issues with the pipes at this point, but I have noticed some condensation on the windows.

1) Am I heating the house to a high enough temperature that I won't come home and notice a pipe-freeze disaster?
2) How can I alleviate the condensation to avoid mould without leaving the doors and windows wide open and letting all the heat out?
3) Which of the following is it more efficient to do to maintain an anti-mould environment, given a constant total heating time of e.g. 2 hours:
-Heat for 2 hours once per day
-Heat for 1 hour twice per day
-Heat for half an hour every 6 hours
-Heat for quarter of an hour every 3 hours
4) Is there anything temporary that I can apply to the windows to keep more heat in that won't also have the effect of stopping up the ventilation and increasing mould that way?

Thanks!

[BookLoverL]

Well... I just realised that in the bathroom (I'd been leaving the door open after showering, but obviously not enough) there was already a bit of mold on the windowsill and it had gone onto the edge of my favourite toiletry bag that I had for years. So now I am seeing if it's possible to clean the mold off that... and I've extended heating time to 1 and a quarter hours twice a day, the next of which starts in about half an hour. There's also a tiny bit of mould on my bedroom windowsill (didn't leave anything on that windowsill). Grr, humid climate...

[bryan]

Pipe freeze: I would personally wrap some carbon fibre heating wire around trouble spots, a layer of insulation around that, and some control system to keep it above freezing, but not much higher.

For the windows, have you considered trying plastic wrap to reduce convection? I haven't used it myself and not sure if it will be useful in your situation (if you open the windows much or if condensation continues even with the wrap).

[chenda]

The room temperatures seem reasonably above freezing so you should be ok...

You want to keep the temperature as constant as possible though to stop the water vapour repeatedly warming and cooling. Also consider a dehumidifier or ask the landlord if they would install vents on the window (cheaper than double glazing)

Wrt to the bathroom does it have an extractor fan ? Because if so keep the door shut otherwise it won't draw properly. You could also rig up some kind of thick curtain to help keep the heat in (in the other rooms that is)

[IlliniDave]

Can't speak to the veracity of this, but I've seen the advice that for example, if you're going to be away a few days in winter to set your thermostat to 55F or higher. The above advice was conventional wisdom in the north central US where in the extreme temps can occasionally fall below -30F. A bit of information that's missing is how cold does it get in your area, where the water lines in your house run (in the house I grew up in, there are no water pipes in the exterior walls except a very short run for the garden hose).

[Frita]

Leaving cabinet doors that house the pipes open when gone and at night, coupled with the heating pipe tape, will help avoid freezes.

You can cut bubble wrap to size, spray window with water, and apply. This will hinder using the window to look out. Another option is hanging thermal curtains.

[BookLoverL]

I'll have to look into getting some insulation for the pipes, then. For the windows, how should I fit any extra insulation so that I'm not removing the ventilation?

As far as I can tell, neither the bathroom nor the kitchen have any sort of extractor fan right now.

The overnight lows outside on the coldest days this week were around -2C (28F) to -3C (26ishF). So, not terribly cold, but certainly cold enough to freeze water. Also, as befits the UK's reputation as a rainy country, outdoor humidity is very high around here, and it looks like it hasn't been under 70% since early December, and there has often been outdoor humidity of 80 or even 90%.

Due to the small size of the house, all rooms have at least one external wall, though the walls are quite thick and made of proper stone as it's a relatively old house. I don't know for certain but I wouldn't be surprised if some of the pipes were at least next to an external wall.

[IlliniDave]

Okay, so if -2C or -3C daily low is a notable cold spell then as a rule of thumb you probably could get by with 10C or so (which is in the range of what you're reporting) without too much worry about frozen pipes, even if they are inside an outer wall. But if -30C might happen, 10C might be too low. But as you've noted, sometimes there are other trade spaces besides the size of the heat bill versus frozen pipes. Where I live we have significant humidity in the summer, so I use the A/C as a dehumidifier.

[BookLoverL]

Thanks Dave, it's good to know that I'm probably not at risk of coming home to a burst pipe, at least.

Does anyone have any thoughts on whether it's better to keep the heating set to come on twice a day for a longer period as it is now, or to change it to come on in a higher number of shorter bursts?

[jacob]

To air out, presuming you have radiative heating (UK IIRC?) rather than convective heating ("central air"), just open ALL windows wide and maybe even the doors for a few minutes until the house is aired out (the old air is out). Then shut them again and carry on. Air does not contain much thermal energy so if the windows are only open for a short while the walls, floor, etc. won't have time to be cooled down by the outside air.

You'll have to do this once or twice a day. If you have convective air, do it when it's off. You can use any heating schedule you like/whatever is comfortable.

[ertyu]

i knew i've always preferred space heaters to ac air because it feels different/better but i never reailzed it's because when you use a space heater the walls themselves warm up

[BookLoverL]

It's all radiators, so that should work. I'll try airing it out tomorrow when it's light again. Thanks!

[jacob]

@ertuy - See lowtechmagazine links in viewtopic.php?p=198948#p198948

[BookLoverL]

So I switched the heating settings to come on for 15 minutes every three hours, which is the same total time as the setting I had it on before for the temperature readings I gave in the first post, but it actually seems to be more effective, because my temperature reading in the room that was previously going between 16C and 12C is now going between 18C and 15C. I made the switchover right after the final long heat that I did. It's possible this way might cause the boiler more wear and tear, I suppose, but it's much better temperature in the house. In fact, after some friends have visited this weekend, I'm going to experiment with reducing the settings to 15 minutes every 4 hours, which is just one and a half hours total per day, and see if it still stays warm enough to stop the condensation.