Attic Insulation - Where do you draw the line?

[Bruce Page]

Our home was built in the mid ‘70’s. To say the rock wool attic insulation is marginal is an overstatement – it’s barely above the 2x4 rafters and in some areas it is below the rafters. The quotes I’m getting are giving me 3 options for blown in fiberglass, R38, R49, and R60, with around a $500 increase with each level. I’m guessing the R38 option would be a huge improvement and I’m leaning towards the R49 option. Would I gain much going to R60?

[Mike Lassiter]

Pitch of your roof is a factor. If you go R60 the perimeter will likely be less due to roof angle preventing you from getting the the thickness needed. The issue becomes return on investment I think. I have 2x6 exterior walls with R19 insulation, R33 in ceiling and R13 in the floor with low E double glazed windows. Our heating and cooling cost have always been much lower than most we know. We also have a auto setback thermostat that adjusts accordingly when we are typically at work. Lived here 17 years now. The fact this double wide had these things was very strong reason I bought it new. It is extremely rare to exceed $150 a month during the year for heating or cooling counting electric. I have a gas furnace.
If you think you will stay several years, I would consider R49 and think compared to what you currently have you will see a vast difference in comfort and cost.
I have been in my aunt's attic which she has lived in about 51 years now. Her ceiling insulation could be 2" thick at best. I can see Hugh improvement in insulating her house too.

[Ken Fitzgerald]

Bruce,

I got an estimate last week and I am waiting for the contractor to call me and schedule fiberglass blown in on top of the rock/wool insulation. I am having R-38 blown in. The R-38 meets local code. My roof is a 4on12 pitch.

[Wes Mitchell]

We had ours done last year. There were/(are?) some tax incentives available, and our gas company had a rebate as well. So be sure to check with your energy companies.

[Pat Barry]

It sounds like my house where I reallly probably didn't even have R19 (6 inches). I bet in most places it was more like R13 (4 inches). Are they saying that they will be blowing in an addiitonal R value of 38, so you would be getting to something like R51 to 57 because of the addition? I would say that's plenty. In fact with that much insulation i think its more important to make sure you have the proper ventilation in the attic (to help keep the attic temperature close to the outdoor temperature)

[James Conrad]

Be sure to ask the install company if they account for settling of insulation, and you may want to consider cellulose. R38 10-12 inches of cellulose or 14-17 inches of fiberglass will settle on average 15%. So, if a product offers R38 at 10" the install depth should be close to 11.5". You could install depth markers of your own to be sure it's done right. If you find out the brand name you should be able to find out the install requierments on the web.

Another point is if you have soffit venting, they should install wind baffles that extend at least a foot above the installed insulation. Otherwise, the insulation will get blown out of the joist/rafter bays along the top plate area. If you have existing baffles, they are probably not the kind that provides for proper blocking of the joist bay to prevent winding.

Also, check with your code official as a permit often needs to be pulled to ensure meeting energy code standards, this should be done by the install company.

[Jerry Bruette]

I'm not a contractor and I've never slept at a Holiday Inn Express, but I've read alot about insulating and ventilating so....

Along with all the other advice you've gotten I'd have the insulators properly plug any openings you have going into your attic, plumbing runs, electrical runs,etc. I'd have them properly cover any can lights you may have also, to prevent any overheating.

I've read that every dollar spent stopping infiltration is worth ten spent on insulation.

And be sure you have proper attic ventilation.

Fine Home Building magazine has some interesting articles about insulating.

Jerry

[Wayne Lovell]

Don't let them talk to you in inches, all blown insulation will settle a certain amount over time. If you look at the bag the insulation comes in there will be a chart on it that will tell you that the bag will provide R whatever for a certain square footage and should be a minimum depth. Insulation contractors are experts at revving their machines up to really fluff up the insulation and when it settles you actually have a lot less R value than you paid for. Calculate the square footage of your attic yourself and then read the bag to determine how many bags of insulation it will take to get the R value you want. Then have a clear written understanding with the contractor that you will get the amount the manufacturer calls for and be their yourself and count every bag they blow in and don't pay them a dime until you have what you are paying for.

[James Conrad]

Good points Jerry. It is code to use a fire resistant caulk or foam on all penetrations, often not required on existing work, but helps stop conditioned air from escaping and can stop furnace back draft problems in severe cases. Whether any can lights are insulation In-Contact rated or not, you don't want to put sealed boxes over them as they will often overheat and shut off.

[Bruce Page]

The bidder I’m likely to go with offered and promoted an attic airseal with 3rd party testing. They seal “electrical, mechanical, plumbing, and framing gaps, holes, & openings” for an additional $1900. They also install baffles to keep the insulation out of the soffit/vent area. I’ll ask about the measuring sticks but I think he mentioned them also. I also qualify for a $500 rebate.

[Craig Matheny]

JUST an FYI make sure that they do not blow the insulation against the eve vents you need the air to circulate...

[Kev Williams]

The house I'm living in was built in '66, my parents bought it in '69... Sometime in the 70's they had the attic "topped off". I've been up there several times in the past few years to wire up new light fixtures and run wiring for security cameras and cell phone boosters (among other things)-- it's a royal pain to do anything because the insulation is so deep, at LEAST a foot, more in some places.

But the stuff works-- this house still has the original single pane windows, I can see traffic drive by in the gap in the front door (yeah, I should fix that!), and even with all the leaks this is the cheapest house to heat in the neighborhood. Just the other day temps got down into the 30's overnight and never got above 50 the next day, without the furnace running, and with customers coming in and out all day, the house never got below 67°. 2 years ago my equal-pay nat-gas bill was $46 a month (gas water heater too). Last year they raised it to $73, but it'll be going down again in June as they were a bit too optimistic...

If ever there was money spent well...

[Brian Elfert]

I just talked to an insulation contractor yesterday morning about insulating the attic on a 900 square foot 1962 house. What I want done is an inch or so of spray foam insulation on the entire floor of the attic to seal any air infiltrating from the house. They would install proper baffles for venting and then put in blown in insulation to R38 or so. They said at least $5,000 for the job. I want to be sure the house never has ice dams. Venting is not good enough if enough warm air is leaking into the attic. The house had new aluminum soffits sometime in the past 10 years and I worry they didn't cut holes in the old soffits for proper ventilation.

My current house I am moving out of has more than a foot of fiberglass insulation in the attic. I could not imagine going up in the attic to do any wiring or anything up there. Luckily, I installed all necessary electrical during construction before the house was insulated.

[Ole Anderson]

If you ever have to go up in the attic, hope they didn't use fiberglass. Even with cellulose, put on a Tyvek suit and wear a respirator. Tape the suit at the legs. Otherwise you will be dragging all sorts of insulation back into the house with you. I know, I've been there with and without the suit.

[Bruce Page]

The insulating crew will be here Tuesday to seal & insulate to R49. We re-roofed, had the electrical service upgraded to 200 amps and had a new furnace & AC installed last month. I'm tired of dealing with contractors, this will be the last improvement for awhile.