Does the ASHP pipe need insulation *inside* an external wall

[joth]

We're installing ashp we plan to use for coming someday too. I've asked the pipes from monobloc outdoor unit to ufh manifold to be 100% sealed armaflex insulated so no risk of condensation forming on it and ruining  ceilings etc

I assume this continuous sealed right through the external wall? This is creating two challenges: how to airtight the junction of the armaflex with the internal OSB skin, and how to cut 2x 70mm 500mm+ deep holes. 

Alternatively we could rely on the OSB as vapour barrier and accept that any condensation that forms inside the wall will evaporate off quickly, given by definition cooling is only used on a very hot day. 

The build up is OSB propassive, traditional B&b cavity wall, retrofit 200mm pavatherm (breathable ewi)

 

Related question: does plastic vs copper pipe make any difference to the risk of condensation when carrying cold water, and which would be better used for the stab through the wall, given it's entirely plastic internal to the house?

 

Thanks

[SteamyTea]

My view is that it is always best to insulate pipework, that reduces uncontrolled losses.

 

Makes no real difference what the pipes are made from with regards condensation, that is a combination of RH and Temperature.

Mechanically it is a different matter.

[joth]

Just now, SteamyTea said:

My view is that it is always best to insulate pipework, that reduces uncontrolled losses.

 

Makes no real difference what the pipes are made from with regards condensation, that is a combination of RH and Temperature.

Mechanically it is a different matter.

 

Thanks! Any thoughts on air tightening the junction where it passes through the wall? Current thinking it so cut the armaflex back, grommet the pipe, and then push the armaflex up tight against the grommet on both sides. This means making an oversized hole though the external wall to slide the armaflex up into (or using say 13mm instead of 19mm though the wall).

 

 

[ProDave]

Seal PIPE to a snug fitting hole in the OSB layer.  Insulate pipe inside and outside tight up to the OSB and seal around that as well.

 

How are you going to use it for cooling?  when I get around to implementing a cooling function it will be by way of a fan coil unit or 2.  For this it will branch off from the flow and return in the plant room which is above the garage.  This means cold water will never flow through the insulated pipes above the living room ceiling, they are only for hot water to the tank and UFH.

[joe90]

With mine (brick and block) I ran the armaflex right through the wall and sealed it both sides with non setting flexible sealant to the bricks outside and plaster Inside, used a core drill with extension fir the hole.

[PeterW]

Drill an oversize hole with 10-15mm all round. Wrap a length of 22/28mm copper pipe long enough to do the wall plus a fitting either end with duct tape and centre it in the hole - wedge with some offcuts of armaflex then use expanding foam to fix it in place from both sides. Trim the foam flush and the tape the pipe to the OSB and then insulate as normal. 

[SteamyTea]

You have to make sure there is no noise transmitted via the pipework.

But basically, make a hole, reseal all membranes, stick pipes through and seal the gaps.

 

[joth]

1 hour ago, SteamyTea said:

You have to make sure there is no noise transmitted via the pipework.

But basically, make a hole, reseal all membranes, stick pipes through and seal the gaps.

 

 

Great point! I'd completely forgotten about the sound/vibration benefit of this approach too. Given the hole in the wall is immediately below master bedroom, making the junction as vibration proof as possible is another benefit of lots of armaflex and squirty foam.

 

 

1 hour ago, PeterW said:

Drill an oversize hole with 10-15mm all round. Wrap a length of 22/28mm copper pipe long enough to do the wall plus a fitting either end with duct tape and centre it in the hole - wedge with some offcuts of armaflex then use expanding foam to fix it in place from both sides. Trim the foam flush and the tape the pipe to the OSB and then insulate as normal. 

 

Fab. Thanks all, and this is a great "work instruction" to give my contractor. 

 

You specifically call for copper pipe. Is this intentional? i.e. plastic is contraindicated for this task? Main contractor prefers copper too, but my ASHP installer wants to use plastic through the wall, and I'm left trying to arbitrate this one.

 

(And our first air-test is happening as I speak, and this penetration is one major omission from that which is now a risk I'm carrying into the final project phases too. I removed the ASHP from main contract to save on VAT and get GHG, but now see the drawbacks of that -- I tool my eye off the ball to let the trades figure this stuff out between themselves which left it undone)

 

 

[SteamyTea]

8 minutes ago, joth said:

 

Great point! I'd completely forgotten about the sound/vibration benefit of this approach too. Given the hole in the wall is immediately below master bedroom, making the junction as vibration proof as possible is another benefit of lots of armaflex and squirty foam.

Our Jeremy Harris put in solid copper between his ASHP and the distribution manifold. Then found it noisy. He then RTFM and found that the reason it came with a coiled flexible pipe was to dampen the sound.

Edited October 29, 2020 by SteamyTea

[PeterW]

18 minutes ago, joth said:

Great point! I'd completely forgotten about the sound/vibration benefit of this approach too. Given the hole in the wall is immediately below master bedroom, making the junction as vibration proof as possible is another benefit of lots of armaflex and squirty foam.

 

 

 

Fab. Thanks all, and this is a great "work instruction" to give my contractor. 

 

You specifically call for copper pipe. Is this intentional? i.e. plastic is contraindicated for this task? Main contractor prefers copper too, but my ASHP installer wants to use plastic through the wall, and I'm left trying to arbitrate this one.

 

(And our first air-test is happening as I speak, and this penetration is one major omission from that which is now a risk I'm carrying into the final project phases too. I removed the ASHP from main contract to save on VAT and get GHG, but now see the drawbacks of that -- I tool my eye off the ball to let the trades figure this stuff out between themselves which left it undone)

 

 

only reason I say copper is that it is is straight and remains rigid. Also it is unaffected by foam unlike some plastics. 
 

I would connect the ASHP to the copper tails with 900mm full bore flexi hoses which should remove or dampen any vibration. 

[joth]

14 hours ago, ProDave said:

Seal PIPE to a snug fitting hole in the OSB layer.  Insulate pipe inside and outside tight up to the OSB and seal around that as well.

 

How are you going to use it for cooling?  when I get around to implementing a cooling function it will be by way of a fan coil unit or 2.  For this it will branch off from the flow and return in the plant room which is above the garage.  This means cold water will never flow through the insulated pipes above the living room ceiling, they are only for hot water to the tank and UFH.

 

I have a fan coil in the loft. I was just going to put the pipes in now but the ASHP installer said he'd connect it for no additional cost so I went ahead and got one. Ask me in 2 months if it works!

 

More info here: