New Ridge vent system
jwyman
| Posted in Green Products and Materials on
Does anyone have any experience with the new Greenward Ridge Vent system? It basically uses Pex tubing in a continuous rolled ridge vent to preheat domestic hot water. Interesting.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Jon,
This system will raise the temperature of the water to a lower temperature than a glazed collector. It's hard to justify the investment in the equipment considering the low temperature of the water it produces.
Additionally, it uses the worst type of ridge vent and restricts air flow with the PEX. If a tree branch lands on your roof, now you've got pressurized water leaking into your attic insulation and collapsing your ceilings.
Sounds wonderful.
I have the system in upstate New York . I did a random spot check last week of the water temp in my storage tank and it was at 116 Degrees F. I'm not sure how hot glazed collectors get but 116 is very hot water plus it's totally invisible from the street. I'm a DIY and installed it with no problems too. I'm going to post a video on youtube soon of the system kicking on when there's snow on the ground, however only kicked on once over the winter. Overall very pleased with the purchase!
I read on their site or the specs that came with it that the NFA was 16.9 square inches per linear foot. I also think they may have partnered with Benjamin Obdyke . My attic is definitely cooler with the ridge vent, I know that for sure. I also only used 2 gallons of glycol in my (closed) loop and have a 40 foot ridge so am not too worried in the event of a leak. My air conditioner has leaked more than that before in my attic.
I saw this product at the GreenBuild Expo and was very impressed with the simplicity and ingenuity of it. I actually held a sample in my hand and it is a very high end ridge vent material and constructed well. I know in Texas my attic is very very hot in the summer months and could see how this product would be a great fit for my community, especially since my Home Owners Association (HOA) won't allow me to install solar panels. Smart idea guys! Bill Woznoski - LEED AP
I have done some research and found out that the complete system is around $6,000. We spent $7,800 on our domestic hot water four panel 120 gallon system (with rebates). I agree that flat plate collectors may be the best option, but as Bill states, this is an option in his type of situation.
Incidentally, I just returned from two trips - one in Orlando Florida and the other in Santa Monica, CA, and in both locations saw far fewer solar installations then here in New England. Much better solar exposure, many less panels.
This does look like a Benjamin Obdyke product, and such products have been independently tested to have only half their claimed net free vent area. Additionally, any ridge vent that isn't externally-baffled will not only allow rain entry but will also reverse air flow direction when the wind blows across them. So, first of all, it's not a good ridge vent.
Secondly, unless you have dramatically insufficient attic insulation, there won't be enough heat loss in the winter to heat the DHW. And, if you live in a hot, sunny climate with an appropriately light-colored roofing, there'll be significantly less heat available at the ridge.
So it seems this is an expensive system designed to work only with inefficient houses and to make the primary function of roof venting less efficient as well.
I recently read about this product in Architectural Record Magazine and am thrilled someone finally figured out how to capture attic heat. The design aspect of it is great too. In my firm we have run into many issues with historical preservation, this is a great example of how to incorporate green building initiatives without compromising aesthetics.
I completely disagree with the comment about the only way the system will work ....is if its coupled with inefficient design and inefficient material. We have built over 50 Homes that have been certified LEED Platinum with HERS ratings averaging in the low 50s. And even with a foil faced osb roof sheathing and light colored shingles and properly ventilated. Our attic temps still Average around 105F and that in Missouri. So you do the math........1+1 still equals 2 Right?
Kyle,
Your attic is at 105 degrees F -- in summer, I assume, not year round.
My solar thermal system with 2 flat-plate solar collectors produces a tank full of 170 degree water at the end of a sunny day. Jon Wyman compared the price of the ridge-vent system ($6,000) with a real solar thermal system with flat-plate collectors ($7,800).
It's up to you, of course. But I'd rather pay a little more and get a real solar thermal system that makes real hot water rather than a system that costs a bit less but only makes lukewarm water.
Interesting system! Looking through the chain if Alex N. can get his system water up to 116 degrees F. that's really all you need. I keep my tank at 120 degrees F. anyways so anything over that is a waste for me. I could also see this system working after the sun goes down because it is still hot throughout the night where a pv thermal system can't without the sun.
J.T.,
It's not a "waste" to have a tank full of 170 degree water. The water is run through a tempering valve or mixed with cold water to achieve whatever water temperature you want (120 degrees, for example). After drawing down a significant percentage of the tank, it may still be capable of delivering 130 degree or 140 degree water.
If a tank connected to a ridge-vent system can get as high as 116 degrees, that's as hot as it's going to get. After the first draw, cold water enters the tank, and it's down to 104 degrees. Each subsequent draw lowers the temperature further, until the heat-collecting loop in the attic can catch up.
This is a brilliant idea! My attic in Arizona reached 150 degrees this week and I have an older broken system on my roof. I can just swap out the ridge vent, use theirs and tie it into my old system. Easy.