Forum discussion
NC-2009 EAp2: Minimum Energy Performance
Hello everyone,
1. Do the insulation requeriment of service water heating pipes (section 7.4.3 and table 6.8.3) apply for any material? The plumbing designer said that CPVP pipes don't need o require to be insulated, however, even in the ASHRAE 90.1-2007 user's manuals these pipes are not excluded.
2. If pipes are embebed in the roof slab, does it need to be insulated? There is no exception about in the ASHRAE 90.1-2007 neither.
Thanks in advance! Best!
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Santiago Velez
ASHRAE BEMP HBDP - LEED GA, Building Performance ConsultantZonda
20 thumbs up
August 19, 2016 - 10:41 am
If pipes meet the criteria on section 7.4.3 a-d, they should comply with minimum insulation.
1. Yes. What is the designer's argument? To my knowledge CPVC has a similar thermal conductivity than PVC so heat loss will be similar.
2. Yes. Unless you want to heat the slab for radiant heating.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5907 thumbs up
August 19, 2016 - 12:31 pm
I agree with Santiago.
Billy Condor
Engineer2 thumbs up
August 19, 2016 - 2:16 pm
Thanks Santiago and Marcus,
The project has some indepedent nonrecirculating storage systems (electric storage water heaters to be specific, with no recirculating pumps), so I understand they must comply with 7.4.3 b and c regarding minimum thermal insulation.
1. Designer says as the project will have CPVC pipes for hot-water service (for showers and some faucets), it's no necessary to insulate these pipes because of its low thermal conductivity (0.16 W/mK), meanwhile for copper pipes are around 380 W/mK. Do you think a quick calculation of the heat loss is needed (maybe just to make the designer realize of it) or just the fact that it is on the mandatory provitions that must be complied?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5907 thumbs up
August 19, 2016 - 2:32 pm
I looked closer. He may have a point. I would think that if you can show that the CPVC pipe has no greater loss than a copper pipe with the minimum insulation thickness then it is equivalent and should meet the requirement.
Santiago Velez
ASHRAE BEMP HBDP - LEED GA, Building Performance ConsultantZonda
20 thumbs up
August 19, 2016 - 4:30 pm
If you go to table TABLE 6.8.3 Minimum Pipe Insulation Thickness, you can find insulation conductivity, which range from 0.032 to 0.049 W/m.K., starting at 1.3 cm thickness. This results in transmittance a lot smaller than your CPVC pipe Im afraid.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
August 22, 2016 - 3:16 am
...from memory there is even a formula for calculating the minimum for conductivities other than standard.
Also look closely at the operating temperatures regarding the exceptions/exclusions.