Insulation Options

16 years ago

I also posted this in the "building a home section" but it may also get some interest here. Sorry about the double post but decision time is near as the builder has made up some time recently.

Our builder is asking us about insulation options and if we want to upgrade. We are jsut outside of Baltimore, MD. Wondering what you guys think of the options (yes/no) and the quoted upgrade costs. 3300 Sq ft, 2 story over unfinished basement, gas heat with heat pump 2nd zone:

STD: The Contractor shall provide and install full fiber-glass batt insulation in all exterior walls 9R-13), exterior overhangs (R-19), garage ceiling below conditioned second floor space and screen porch ceiling 9R-30), and exterior foundation walls (R-11), and blown or batt insulation in second floor ceilings 9R-38).

R49 in Attic $500

BIBs insulating system $2200

Flash and Batt $2650

We are being advised against the "Flash and Batt" since we wnet with SIS board construction instead of plywood and wrap. Have been told the house would be too tight and need a makeup air $y$tem. Thoughts?

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Comments (4)

jakethewonderdog
16 years ago
Well, this is a tough one.

I can give you some general guidlines:

1. You should insulate and make airtight and then add ventilation if needed. You don't want to "build in" ventilation.

2. The BIB system can be better than regular fiberglass... but fiberglass can become less effective at lower temps because of convection in the fiberglass. A high density cellulose application can fill voids just as blown in fiberglass can, but can have a better R value when it gets cold.

3. The Flash and Batt (I'm assuming this is an inch of closed cell foam with fiberglass batt insulation) can be very effective esp at reducing air infiltration with a lower cost than 100% foam. Closed cell foam has a higher R value per inch (about double)than fiberglass. It also doesn't diminish as it gets cold like fiberglass does.

Other things that enter into the equation:

How much are utilities in your area?
How long will you be in the house?
Will the insulation upgrades result in a smaller hvac system?
If using SIS board, how thick is it (how much R value)? You will start getting into diminishing returns at some point with all of the insulation.

I will also say that the quality of the installation is going to matter a lot at this point. A sloppy job of insulating or installing the SIS boards is going to really hurt how well the system performs.
countryboymo
16 years ago
I think I would at least upgrade to the flash and batt. I wouldn't worry about the home being 'too sealed' It takes a whole lot less energy and money overall to add ventilation than what you pay to keep the temperature regulated. If the money is there I would do the flash and batt and attic additional insulation.
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wannabchef
Original Author
16 years ago
Thanks for the input folks!

Jake - The SIS we are using is the 1/2" R3. How can you tell a good job from a sloppy one? The diminishing returns is what I am wondering about. I realize that more is better but only to a point. If the DOE (I think) reccomneds R13 and with the SIS I am at R16 - does it really help to go to R22 for the additional $2200??? Not looking at changing mechanical components if we do extra insulation.

CC
wannabchef
Original Author
16 years ago
Jake - to answer a couple of your other questions:

Electric (A/C) is $0.1197/kWh and Gas is $0.65/therm

How long will we be in the house? Good question but I would think 5-7 years is an easy given.