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bluefoxicy 07-20-2013 12:21 AM

Insulation plan
 
Okay, done some research.

I have a ton of heat coming in. Like I have a 14,000BTU air conditioning unit in a 225sqft room. It can't keep up on a 90F day. 14,000BTU can cool a 400sqft room; my insolation is like 4-5kW. You can imagine the discomfort and the costs; I'd need a 5 tonne unit to cool my tiny, tiny little town home. The TLD shows me that the wall in the bathroom is 81.6F, and the ceiling 2 feet above that is a whopping 90.3F!

What I'll do right now, since I have so much heat coming in, is paint my tar built-up roof with a roof coating to reflect radiant heat away. My roof is not shingled, it's a strange sort of thing.

Following that, I'll be repairing the ceilings here. Foregoing blown-in insulation, I've decided to go with mineral wool batting over fiberglass. Fiberglass costs half as much, but mineral wool is much less toxic and better performance. Real sheep's wool costs 5 times as much and lasts 50-100 years, but it's too pricey. Mineral wool is moisture resistant (sheep's wool is moreso) and mold resistant (sheep's wool is completely mold resistant).

The whole plan will include a separate vapor barrier above, as well as a radiant barrier stapled to the rafters. It's too hard to install it properly above the rafters in an existing roof; stapling it to the rafters, below the wool insulation, is a valid location but less optimal. 5/8 inch drywall ceiling to finish, because I can't get 1 inch thick drywall. Exterior walls will get the same treatment as the ceiling: Vapor barrier, batting, radiant barrier, thick drywall.

The main bedroom has a huge issue with heat coming in through the floor, above the porch. I'll put foam panel sheathing on the exterior; a radiant barrier if possible; vapor barrier; 7.5 inch batting (wide space means I can use the R-30 stuff instead of R-23!); then another radiant barrier because it's cheap (it's $70 for like 500sqft); and permanent subfloor above that. Total R-Value should be 35 plus radiant barrier (I could use 2 inch sheathing for its R-10 instead of R-5... not sure if I should). Most of the transmitted heat will be radiant, so the radiant barriers should perform exceedingly well here.

I'll probably take the opportunity to apply acoustic insulation to the walls and floor in that room as well. I can hear outside quite clearly with all the windows closed, as if the windows are wide open or just standing on a balcony. I listen in on peoples' conversations in detail on their porches down the street 5 houses.

Assuming the baseline is just fiberglass batting plus vapor barrier and the roof coating (which extends the life of the roof anyway), the additional stuff will probably cost oh... for the one room? $115 for the radiant barriers (three covering 225sqft), an extra $350 in batting insulation (ceiling, floor, and walls), plus $45 for the outside sheathing. So kicking it up from basics will cost me $510. The whole project should cost me about $1260, plus drywall and subfloor ... about $1600-$1800. So I want $3000 on hand total before I begin.

I'll get a better estimate by doing a work breakdown structure, producing a bill of materials, time estimates, and citing out any contractor work I want done on the WBS. But I'm thinking under $2000 for this.

Thoughts?

gregzoll 07-20-2013 12:43 AM

If all you are using are window units, they will not keep up for nothing in this heatwave.

As for the roof, you are better to get something like this for your roof http://www.siplast.com/HC/Products/R...20Systems.aspx

http://www.roofingcontractor.com/articles/84778

You need to also properly insulate any attic spaces that you can with blown in, due to using Mineral batts over Fiberglass batts is not going to do anything for you. Even better would be to go with a Closed Cell blown in foam.

Also helps to update in your profile where you live, and how many rooms in this place, type of construction, if you also have Central air, or just using portable window units.

bluefoxicy 07-20-2013 08:14 AM

Quote:

Originally Posted by gregzoll (Post 1218234)
If all you are using are window units, they will not keep up for nothing in this heatwave.

They're doing well enough as-is to keep the house not terrible. One failed (tripped a breaker) the other day and it dropped the house from 95 to 84 in 45 minutes, but no further (it's set to 76). The big issue is a huge amount of incoming heat; central air will be the next step, but it's expensive and expensive to run.

Quote:

As for the roof, you are better to get something like this for your roof http://www.siplast.com/HC/Products/R...20Systems.aspx

http://www.roofingcontractor.com/articles/84778
I've looked at white/aluminum (shiny) stuff. The issue is 95% of the sun's light isn't actually visible; it's in IR. You can apply a completely black roof coating and reflect more heat away than a white coating if the white coating isn't reflective in IR and the black coating is.

The problem, of course, is I don't know the difference between any of this stuff. When I lived with my parents, my dad picked out a metal colored one because it was shiny and he figured reflecting light = good, and it was minimally effective. It was effective though.

Quote:

You need to also properly insulate any attic spaces that you can with blown in, due to using Mineral batts over Fiberglass batts is not going to do anything for you. Even better would be to go with a Closed Cell blown in foam.
Mineral batts have a higher R-value, but are also not as toxic as fiberglass. There's a lot of advantages. Notably, fiberglass settles over time much quicker and more significantly than mineral; and is more affected by moisture. Blow-in is good if it doesn't settle; but installation of good blow-in is somewhat more involved (it involves spraying water into the area...dry blow-in insulates less and settles more over time) and requires some measure of skill. You can't screw up batts, but they are less effective--40R blow-in versus 30R batts, yeah.

In this case, I've decided I'd rather deal with fewer moving parts and less risk of incorrect installation. I simply don't have the experience to install blow-in.

Quote:

Also helps to update in your profile where you live, and how many rooms in this place, type of construction, if you also have Central air, or just using portable window units.
Baltimore.

3 bedroom, 1 big front room downstairs, 1 12x12 kitchen, basement.

Town home, middle unit. End unit is burned down and will likely be torn down.

Just window units. Will get a heat pump later, but that's a way off. Using a heat pump into a thermally open toolshed isn't going to help.

gregzoll 07-20-2013 12:54 PM

As for toxicity, it will not matter, due to the outside environment is more toxic. Mineral batts are good for keeping noise down, but for insulation, you need to either use Foam board, blown in if enough attic space to get up there, or Closed Cell foam applied to the roof sheathing from underneath.

As for that unit blowing the breaker, it did it, because either the compressor in it is going bad, wiring is wearing down, and the water splashing up caused a short, or the fan motor windings are wearing out, if it is a very old unit.

As for that roof covering, it does work, and well worth the investment to help keep some of the solar gain down. Majority of solar gain comes from the roof, then if the attic insulation is not proper, it radiates off the building materials.

Personally if you are unable to pull duct lines through the attic space for a high velocity split system, I would look at mini-split zoned system for the place.


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