RIP: Solar Powered Attic Ventilator’s

Welcome to a new series, based on putting numerous bad building practices and so-called green myths & misconceptions to rest. While I wish I could take credit for this idea, I do have to give the credit to this week’s – Let’s Blog Off. Needless to say, it was supposed to be based on writing one’s one obituary and limited to 208 words, but seeing there are not any real rules – why not change it up some? With that said, we will have a list of all the participating bloggers at the end and based on a few comments I have heard, they ought to be great.

RIP: Solar Powered Attic Ventilator (aka SPAV)

SPAV, 1980’s – 2010, a key figure in costing the average homeowner $800 a pop died this day from complications brought on by Acute Respiratory Distress Syndrome (ARDS). While touted in some well known publications like the 2005 Building Products Magazine as one of the Most Valuable Products, it unfortunately never managed to live up to any of its hype.

SPAV is commonly touted utilizing such misleading messages such as its ability to cool an attic, preventing ice dams, and eliminating moisture problems. While the pages sound great and are filled with some well-known building science data, the problem is that the same science has never proven their worth. In many cases, these units are specified in leaky, under-insulated houses that can cause depressurizing causing possible combustion safety issues, radon issues, and sending that costly air-conditioning outside.

While many warnings of ongoing issues were provided as far back as 1995, the SPAV coolly dismissed them. Now it is commonly found being listed on many sites under the Useless Products List (#5). Unfortunately, rumors abound that this is not sitting well with those that have made fortunes off selling them and they are fanatically denying its death.  Ahhh well, I guess somebody will always chase after an easy dollar.

While this article is partly written in jest, there are major issues with simply believing the hype. For example, while I do not live up north, I really do have to ask – can anyone tell me how a solar powered fan (especially with a thermostat) buried in snow is going to help prevent ice-dams? Can anyone tell me how pulling in the hot humid air here in the southeast, will lower the moisture in the attic? I got news for you; in both cases, it does not and will generally exacerbate both of those conditions.

Now many people will argue the point that the test was compiled back in 1995 and we should do new testing. To some extent, they are right, but oh so wrong as the same issues listed in the original study still exist today even in newer homes. With that stated, there are a few areas where a fan like that does make sense; like a roof where one cannot add in the required ventilation at the upper section. If you have an existing house & are noticing that your attic is hot as you jump on a step stool and can feel the heat radiating down, notice weird melting patterns of the snow on your roof, or can just feel the heat or coolness before you go to open up the hatch, there are some places where your money will probably be better spent.

  1. Have your house tested with a blower door and eliminate air leakage between the attic and living space.
  2. If your attic hatch is extremely hot, it needs weather stripping and insulated with either a foam box covering or foam directly applied to it.
  3. If you have air ducts or an air handler located in the attic, at minimum you should have your duct system tested, sealed and insulated.
  4. Make sure all the baffles required are installed and insulate the attic floor to a minimum of R-30 (or what the codes dictate for your area) after air sealing.
  5. If you are replacing the roofing, look for ENERGY STAR® shingles, metal roofing, concrete tiles (aka the Cool Roof Option) & make sure the proper amount of ridge and soffit passive ventilation is installed.
  6. If you are not replacing the roofing and an inadequate amount of venting is installed, bring in a professional to help evaluate and perform the proper retrofitting work.
  7. Consider going with a hot-roof system

Ok, and now to see who played fully by the rules… (and for the record – 207 words for the actual obit)

  • Joseph

    Well, OK, if it’s going to be that kind of obituary, you really should have written it on the people who go door-to-door selling home improvements! None of those fly-by-night clowns do anything but take your money!

    • SLS Construction

      Sorry, but I don’t think anything will kill them off until people learn — in regards to this subject – we want pics of that kitchen

  • Ron

    As with every negative comment I’ve read to date. There is more to this then you’ve been led to be accounted for. On the whole you are correct, most solar fans will not perform as advertised. But there are some that do, and there is documaentation to prove it. please check out @ solardynamicsinc .com, and give us a call. We’d be happy to fully explain

    • SLS Construction

      Ron, I do like the idea of the battery to help keep the fan running optimally, but you still have some claims on there that just don’t fly. Save up to 35% on your cooling, virtually eliminate moisture problems, etc… Oh wait, I can’t top this one – “Originally developed for the extreme climates of Hawaii”
      I love it – Hawaii with it’s average highs in the 80’s year-round – sounds like a tough design assignment.
      Like I said above, there are places for units like this (and yes I will actually keep your’s in mind due to the battery), but by and large their money is better spent fixing the real issue and not trying to mask it with a band-aid.

  • cindy frewen wuellner

    Amen and amen. here’s to refuting ridiculous claims with humor and facts. Excellent obit, Sean. You’re the real deal, passionate about crappy building products. cindy @urbanverse

  • stevemouzon

    This is really good… One question: is SPAV really the official acronym? If so, then wow… what a name to have! No wonder they bit… err… will hopefully bite… the dust!

    • SLS Construction

      Thanks Steve & to answer your question – it is a combination yes & no. A PAV is a commonly used acronym for Powered Attic Ventilaters. I have yet to ever see an accronym really used for their Solar counterparts. Occasionally I will see the terms Solar PAV, it being fully spelled out, or most commonly – a Solar Attic Fan.
      I know in Georgia, as Allison below can attest – the Powered ones are being outlawed.

  • Chamois Green

    This is probably the only educational obituary I have or ever will read! Interesting take on our topic – I can now say that I’ve learned something. (Hopefully I will remember it when I have my own house in the future!)

  • Anonymous

    Good one, Sean! I wrote a guest post for the MS Hohm blog about this a while back that generated a surprising number of negative comments. Here are some good links that support what you’re saying:

    If you’d like to see what other building scientists say about this issue, read this article at by Peter Yost:

    Or you can download this paper from the Florida Solar Energy Center reviewing the research not only about attic ventilation but also about sealed attics with insulation at the roofline instead of at the flat ceiling:

    • SLS Construction

      Thanks Allison, I swore you had wrote one that I wanted to refrence but could never find it on your site, now I know why. The biggest problem with articles like this, is how deeply engrained certain “truths” or experiences are ingrained in some, much less understanding when something that is great will be bad & vice-versa.

      • Anonymous

        You’re welcome, Sean. Yep, that’s why you couldn’t find it. I’ll eventually post that article in our blog, but I’m waiting for the hot weather to return before I do that.

  • Jake

     I second this. I have two of these solar attic fansfrom US Solar and have noticed zero difference in my attic temperature. The sun beating on the roof tiles seems to do more heat damage to the inside of the attic than these weak fans can exhaust.

  • Bob Blanchette

    I’ve always wondered about the CFM ratings on the fans. Only in solar attic fan world can a 20 watt motor move 800CFM of air.

    • SLS Construction

      Yep, got to love their math – basically though it is based off the size of the opening & the fan is just there to simply assist it
      Thanks for joining in & commenting – much appreciated

  • screen_doors

    For people who have already gone through all those checks, and found the results satisfactory, good for you. Some might even feel that their house is still cold despite those checks and insulators put in place. Having screen doors might help with thermal control and heat loss, so it is an option too.