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DIY Solar Water Heating: Do I need to Reinforce my Roof?

 

Advice provided by: Rob Freeman Jr, LEED AP, Green-Buildings.com
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Marc asks: If I install a solar hot water heater (solar thermal system) on my roof, do I need to reinforce my roof?

Answer: Hi Marc, it's my understanding that the weight of the average photovoltaic system (PV) is about 3 lbs per square foot. Solar hot water heating equipment can weigh significantly more. However, most roofs are designed to withstand the weight of a 200 lb person moving around (called a live load) so, assuming your system is less than 200 lbs per sf, your roof should be OK to accept your solar collector without reinforcement.

Many DIY solar collector panels weigh about half of what the live load requirements are on a typical roof (or 100 lbs).

In placing your solar HWH panels, make sure they're positioned to gather the most light and, if possible, try to keep them from being visible from the street as there (unfortunately) is plenty of NIMBY activity with solar and PV.

Hope this helps!

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Expert Advice and Comments

Solar Hot Water

Mon, 03/22/2010 - 08:41 — Allan Miller (not verified)

Hi,
The weight of a solar hot water system with the tank integral to the system can be 450kg depending on the capacity of the cylinder.
Does this require the roof to be reinforced?

RE: Solar Hot Water Heater and reinforced roof

Tue, 03/23/2010 - 15:53 — GBGuru

Hi Allan, if the system you're considering weighs 450kg, it could mean reinforcing your roof is a good idea. There are 2.2 lbs per kg so that's about 1000 lbs which is much more than a typical roof is designed to handle in a concentrated spot. I don't know how much surface area that system covers, but you may want to check with a structural engineer or your local building department before going ahead. Best, Rob

Thanks for the blog I do not

Thu, 04/08/2010 - 08:39 — Jason Alen (not verified)

Thanks for the blog I do not know that for solar hot water heater I need to reinforce my roof.

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Mon, 03/19/2012 - 07:18 — los gatos Plumbing (not verified)

Great article …Thanks for your great information, the contents are quiet interesting. I am looking forward to your following post.

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