Insulating Raised Water Tank in Loft

Discussion in 'Plumbers' Talk' started by Eric P, Feb 6, 2021.

  1. Eric P

    Eric P New Member

    Hello All,

    Probably a bit late to be asking these sort of questions with the snow due tomorrow morning but I am looking for some advice and guidance on insulation in my loft in regard to a cold water tank that is sitting on a platform raised above the ceiling joists by about 2 foot/30-50 cm.

    I have a fairly old style hot/cold water system in my house, massive cold water tank in the loft, immersion heater in the kitchen and the house heating system is electric storage heaters (no gas connected).

    The loft was insulated a few years ago with loose fill insulation but the trapdoor was just a bit of badly fitting MDF and the space under the water tank was left empty except for a a couple of cm of the old insulation that was there when I moved in about 20 years ago. At the same time as the loose fill insulation was installed I put new polyethylene pipe insulation around the pipes and insulation blankets around and on top of the water tank. Finally, just under where the pipes exit from the water tank I have also placed a small tube heater that I have on during the coldest months.

    Jumping forward to December 2020 I had to have some roof maintenance carried out that has included the installation of tile vents to remedy a condensation issue. At this time I decided that this would be a good opportunity to redo the loft hatch and I now have a snugly fitting plywood lid resting on foam pads to give a snug seal and 150mm of solid insulation on the top.

    Now to get to the main point. At the same time, and this is what I need advice/comments with, to better direct the warm air from the room under the cold water tank I made a box made out of 100mm solid insulation panels to create a tunnel effect to direct warm air from the room below directly onto the underside of the platform where the water tank sits and prevent any of it escaping into the rest of the loft area. Is this a good idea, or is it stupid and am I asking for trouble? Will this keep the tank warm and/or could I risk causing condensation inside this box and damaging the ceiling and/or platform?
  2. rogerk101

    rogerk101 Screwfix Select

    For a header tank to freeze would require temperatures to drop well below freezing and not rise above freezing for a week, so I wouldn't worry. The really cold weather is only due to last for about 3 days, and it's unlikely to drop below -5 at its coldest, but it should rise above freezing during the day. Unless of course you live up in Scotland, but if you did, you wouldn't only be coming for advice now ... you would have done it a week ago.
    If you really are worried, leave a tap on really low flow in, say, an upstairs bathroom. One drip every few seconds should keep enough of a water flow to prevent the ball cock mechanism from freezing.
    Eric P likes this.
  3. Eric P

    Eric P New Member

    Update: I decided to get a remote thermometer so I could monitor the temperature (and humidity) in the loft and I was rather surprised to see that the temperature didn't drop below 4 degrees in the loft despite a very reasonable amount of insulation and it being -9 outside at the same time. Looks like I was worrying unnecessarily but I guess better to identify a potential problem than have to address a failure. I will consider installing pipe heaters for next year but it is probably overkill. (@rogerk101, thanks for the tip about the taps)
    rogerk101 likes this.

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