[WattWatcher]

OK, my test worked so here goes...

Greetings everyone! I'm a new member and I think it took me four hours to go through all of the posts going back more than three years! I commend and thank all of you for keeping the conversation going for so long with such camraderie and enthusiasm.

I have a few comments before I introduce my own situation with HRVs. First, if any of you who have successfully built working devices are interested, I encourage you to post detailed instructions on instructables.com, or some similar site, where many more people will be able to access them easily. Second, it would be great if someone compiled an "HRV lessons learned and great links" thread. The bottom line is that the vast amount of information in this thread is too dispersed and difficult to access, considering the digital age that we live in.

Regarding HRV designs, I don't have much to add to the conversation (at least not yet), but I did come across some materials that I don't think have been mentioned here. There are three different types of signage material similar to coroplast, but with aluminum on the exterior instead of plastic (the corrugated core is still plastic). These are called Alumalite, D-lite, and Econo-lite, Unfortunately, they are all rather pricey, but they would probably offer somewhat better heat exchange than coroplast.


My situation is the following: I live in Berkeley, CA and I have a 300 square foot cottage in my backyard that is a converted garage, and which I rent to a single person. The climate here is very mild and on the cool side, known for our foggy summer mornings. In the winter, the daily temperature generally goes from 4-13 C and in the summer from 13-22 C. The cottage is an uninsulated, concrete block building (except the roof is insulated), that has one large space with a kitchenette, and a small, separate bathroom. In its present state, the cottage is very inefficient in terms of heating (it's heated with a modern natural gas space heater).

I'm planning to add insulation and drywall to the West and North walls, and possibly make the South wall into a Trombe wall (it has very good solar exposure), put in double paned windows and add a layer of insulation and laminate flooring on the concrete slab. The cottage tends to be damp, especially in the rainy season, and that's why I want to put in an HRV. Since the space is only 300 square feet, I think the HRV only needs to have a flow rate of 20 cfm or so.

My quandry now is whether to buy a unit or go DIY. All of the commercial HVRs that I have come across are much too big for such a small space. Through this thread, I learned about the Panasonic WhisperComfort™ Spot ERV. It has a very low flow rate, low energy consumption and it's very reasonably priced. However, it is an ERV, so my concern is that it will not remove enough of the excess humidity that I want to get rid of. I spoke to a sales rep at Panasonic today, and he said that the Whispercomfort would only pull moisture out of the interior air when the humidity is higher indoors than outdoors. That sounds pretty good to me, but I'm not sure. Perhaps I should start by measuring the indoor and outdoor humidity over a period of time. Can any of you shed some light on this issue? Most of the info I've seen online, as well as in this thread, pertains to places with more extreme climates than what we have, so I need help conceptualizing how this ERV would perform in my situation. If I can get to a place of feeling like the Panasonic will do a good job, then I'll probably buy one. But, I don't want to make that investment and then find that the cottage is still too damp afterwards.

On the DIY side, I really like the results that some of you have gotten with your HVRs. My main two concerns are that I have so many other projects brewing that adding the HVR would be burdensome (I want to have a working HVR within six months). I also wonder whether a DIY HVR would be reliable in the long term. Also, I am not living in the cottage, and I don't want our tenant to be too much of a guinea pig, especially since ventilation does affect one's health. If I decide not to go DIY for the cottage, I still have the option of making one later for my clothes dryer exhaust (another great idea from this thread!) If I do go DIY for this project, I also wonder how to size the heat exchanger.

Thanks, in advance, for your advice!