Insulation under DHW cylinder

[Elf]

Hi all,

 

I need to install a new 300L cylinder into a passivhaus.  Looking at the telford tempest, it has an energy rating of "C", so not the best (considering telford as it ticks off most of the other features needed).  Im going to wrap it in extra insulation after the fact to improve the heat losses a bit.  But I cant improve heat losses from the cylinder base this way.

 

My question is: should i put any insulation under the cylinder, and if so - what should I use?  My idea is to use some load baring insulation, put it direct on the floor and then put the cylinder directly on top of this.  This would lower heat losses through the bottom - the only part I cant wrap insulation around after the fact.

 

Is there any reason why this  may be a bad idea?

 

If I go ahead - Im thinking foamglass or maybe XPS insulation - but any other recommendation gratefully accepted, neither of these are ideal really so looking for other options to add to the mix.

 

Thanks.

[Conor]

I put our cylinder on a 75mm thick slab of compactfoam that I had leftover from our door blocks. This was done for practicality reasons, cylinder had to be installed before floor was screeded, and coundlt sit on the PIR. The savings will be minimal tho as the bottom of the tank is almost always cold and is a small surface area compared to the reset of the tank. Dont worry about it.

[RobLe]

Our DHW tank itself was extra insulated with sheet insulation cut and glued into place to form a box, poly beads poured in behind.  There's still plenty of excess heat from valves and pumps and stuff to dry socks with.  But now socks don't get lost round the back of the cylinder:-) 

[JohnMo]

I would put the cylinder on a stool, and infill the stool with insulation. Cheap and easy to do.

My cylinder.  Made pads/cushions out of leftover airtightness vapor control membrane and left over glass wool.  Boxed in piping, heat exchanger with leftover PIR.  Mine is on the floor, but the floor/ceiling has 100mm of insulation in it.