[owly]

Originally Posted by aardvarcus

Teoman,
I have built two. Another one of my hobbies. All you really need to do is achieve very high R values in the floor, walls, and ceiling and do good air sealing. Stay away from scam products that lie about R values. Radiant barriers and air sealing products are bad about this, they work but their effects can’t be quantified in terms of an R value. You don’t need fancy products, just add more of the same insulation for what is usual in your area for construction which keeps the cost affordable. I had to quit posting on energy efficient housing forums as this advice is contrary to what lines the pockets of the forum sponsors.

They look just like normal houses, except the exterior walls usually end up very thick. For example my brick faced double stud wall is 21 ¾” thick and has a true R-67 after discounting for thermal bridging. Insulated with Recycled (used) polyisocyanurate foam (unbelievably cheap, get fiber faced not foil faced for moisture reasons) between the stud walls and fiberglass. The internet is full of wisdom here (search Passive House), you just have to shovel through the garbage. In order to transplant a design from one climate to another you must pay attention to humidity and moisture. Do not just grab a design from up north and build it down south.

Use fewer larger windows (save cost for same amount of light) and spring for triple panes or better. (Vinyl replacement triple panes are affordable, only 10-20% more than similar double.) Get the R values high enough and all you need to condition the space is one or two mini split air conditioners. Lighter exterior colors and cool roofing products reduce the temperature of the outside surface, aka if you want a dark exterior you need even more insulation to get the same performance.


Redpoint5,
I was talking about phase change solutions, usually waxes or salts, sold in packets and marketed as PCM. I can’t explain it either, but the data sheets show a drop of in performance after a number of cycles. I assume the chemistry degrades over time? Obviously normal materials don’t normally stop absorbing heat when they phase change…

The problem being is that if you need a specific temperature of phase change there are relatively few options other than those solutions. I purchased a quantity of PCM packets that change phase at like 40 degrees for my refrigerator due to the monthly power outages in my rural area. Got to keep the fridge cold until I have time to start the generator.

Oops........ I didn't read this before posting. It should have been a "qualified" statement from the start.


H.W.