Insulation required around flow and return pipes (inside the house)

[markharro]

Hi I know that the pipes need to be well insulated once they exit the external wall between the wall and the fan unit but does the pipe run once it is inside the house from the penetration points to the hot water tank does this pipe run also need to be insulated (in a passive house)?

 

thanks

[IGP]

 

[JamesPa]

Both building regulations and MCS rules have something to say about this. 

 

Under building regulations, in a newbuild, the answer is that primary circulation pipework must be insulated where it is 'outside the heated living space'.  In a retrofit this applies to only to accessible DHW pipework.  'The heated living space' excludes 'voids'.

 

MCS rules (specifically MCS3005 - D clause 5.6.7) prima facie go further than building regs in the case of a retrofit, and require distribution pipes to the cylinder (if the cylinder is replaced) to be insulated whether or not they are accessible.  However I argued with them over this and they conceded that the ambiguous text should be interpreted to require insulation in retrofits only where accessible.  Here is a screenshot of the communication from MCS which also includes the relevant extract from  building regs.

 

 

Here for reference is the relevant extract from MCS 3005-D

 

 

Edited October 23, 2023 by JamesPa

[Dillsue]

3 hours ago, markharro said:

 does the pipe run once it is inside the house from the penetration points to the hot water tank does this pipe run also need to be insulated (in a passive house)?

If its a feed to the hot water tank, you'll likely want the heat from the heatpump to go to the tank rather than heating the air even if its within the thermal envelope. If the pipes aren't insulated you're giving the HP more work to do at a time when it'll likely be running at a poorer COP heating to a higher temperature for the hot water.

[markharro]

Thanks @Dillsue and I think that this also reflects the point in the Heatgeek video which is that if you dont insulate the pipes going from the fan unit to the hot water tank then in the summer you are heating the house over this pipe length when you may well not want to do this!

[HughF]

I Insulated all the primary pipework to the cylinder cupboard, and will continue to insulate as much as I can whilst the ceilings are down.

 

Fully insulated from the ashp to the cylinder now, close to 25m of pipework.

[TonyT]

You don’t rely on the uninsulated  pipework to heat your house, so insulate it to keep efficiency of the heat system higher/reduce these losses

 

 

[HughF]

If you ever want to cool in the summer, you should definitely have your pipework insulated.

[markharro]

To renew this thread we are shortly to have our HW cylinder installed and connected up to the flow and return pipes which will then be getting insulated - question: is there a standard thickness/type of foam insulation to use around the pipes internally? thanks

[JohnMo]

33 minutes ago, markharro said:

standard thickness/type of foam insulation to use around the pipes internally

 

I use 25mm if available, but mostly 19mm.