Green Building Forum - Heatloss from tank to room: effect in degrees against U-values of insulation... Tue, 09 Jun 2026 08:20:19 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Heatloss from tank to room: effect in degrees against U-values of insulation... https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143031#Comment_143031 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143031#Comment_143031 Tue, 17 Apr 2012 11:12:35 +0100 James Norton
- Basically insulated DPS thermal store (say @ 80deg)
- Addtional insulation by me
- in and insulated cupboard
- in a bedroom

How to work out the heatloss over say 24 hours and the effect on temperature in tank vs room...

Can I do this as a steady state do you think? on the basis that the temperature gradient although varying will not vary much in absolute terms over 24 hours?

J]]> Heatloss from tank to room: effect in degrees against U-values of insulation... https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143044#Comment_143044 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143044#Comment_143044 Tue, 17 Apr 2012 12:44:46 +0100 djh Posted By: James NortonHow to work out the heatloss over say 24 hours and the effect on temperature in tank vs room...
I guess it depends how accurate you want to be. If you just work out the U-value of the insulation as if it was all flat layers and then use the external surface area (i.e. area of cupboard walls) that should give you a worst case. There are formulae for calculating cylindrical insulation for pipes if you want to make a closer estimate.

Edit: To calculate effects on temperature: for the tank, you calculate energy stored in the tank (specific heat x volume x delta T) and subtract your heat loss to calculate the new temperature. For the room, you need to do a calculation of heat losses to the outside and to other parts of the house, which is more complicated. It's probably easier just to think of the tank's heat loss rate as an extra heater added to the room - if it was say 1 kW, you can guess what the room would feel like.

Can I do this as a steady state do you think?

I would think so. But if you do the calculation in a spreadsheet, it shouldn't be too hard to do multiple estimates at hourly intervals or whatever.

If you find that the bedroom is going to get too hot in the summer, you might consider leaving a one or two inch air gap around the insulation inside the cupboard. Then you could vent it outside in the summer, and keep it sealed in the winter.]]> Heatloss from tank to room: effect in degrees against U-values of insulation... https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143045#Comment_143045 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143045#Comment_143045 Tue, 17 Apr 2012 12:54:47 +0100 James Norton
J]]> Heatloss from tank to room: effect in degrees against U-values of insulation... https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143098#Comment_143098 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143098#Comment_143098 Tue, 17 Apr 2012 20:40:33 +0100 SteamyTea If real, then measure it, if not then spreadsheet it.
You could treat the tank as a heater, and the room as s semi infinite heat sink. So as the tank cools, the room warms, reducing the ⌂T.

The posh way is to use Newtons Law of Cooling (and heating) and subtract one from the other at either know time intervals or known temperature intervals. Then plot the results.

End up with something like this:]]> Heatloss from tank to room: effect in degrees against U-values of insulation... https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143114#Comment_143114 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143114#Comment_143114 Tue, 17 Apr 2012 21:57:01 +0100 djh Posted By: SteamyTeaIs this an academic exercise or is it a real one.
If real, then measure it, if not then spreadsheet it.
Clearly you're a Fred Hoyle supporter and possibly even a believer in Gödel's universe.

The insulated tank is real, just not yet! This is a design discussion, in advance of implementation. Generally considered a sensible idea! But it's difficult to measure something that doesn't yet exist.]]> Heatloss from tank to room: effect in degrees against U-values of insulation... https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143116#Comment_143116 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143116#Comment_143116 Tue, 17 Apr 2012 22:01:14 +0100 DamonHD
Rgds

Damon]]> Heatloss from tank to room: effect in degrees against U-values of insulation... https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143133#Comment_143133 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8959&Focus=143133#Comment_143133 Tue, 17 Apr 2012 22:48:52 +0100 SteamyTea Posted By: djhThe insulated tank is real, just not yet! This is a design discussion, in advance of implementation. Generally considered a sensible idea! But it's difficult to measure something that doesn't yet exist.
Getting very Zen like this is :cool:

Or Schroedinger's cat even (where what works at the small scale does not at the large scale)]]>