Attic insulation

Last updated February 15, 2013



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Energy efficiency | Raising the floor | Insulation | Cost | Ventilation | Additional work

The house that Norma and I own is heated by oil. Our boiler is serviced by Laurel Fuel Oil and our fuel is purchased from them too. They have provided good service and their rates seem reasonable. However, the amount we pay each winter seems unusually high for such a small house. This could, in part, be due to the fact that our Weil-Mclain P-366 boiler is about 20 years old. But it still works fine so it is hard to justify spending a couple thousand dollars to have it removed and get a new, more energy efficient one installed. But that is not an option we have yet to discard...just a last resort.

Energy efficiency

How do we lower our energy bill without purchasing a new heater? By making the house more energy efficient, of course. The question is, how do we do this without spending a lot of money? And if we do spend a lot of money, how do we make sure we get a quick return on our investment?

When we first bought the house, we didn't know if there was any insulation behind the walls. The previous owner didn't even know this. So I drilled 1.5 inch diameter holes into several walls. I discovered that the walls on the north side of the basement do not have insulation. These walls are panel board placed only an inch or so from the cinder block. The downstairs bathroom and the laundry room in the basement have cinder block walls so of course they are not insulated. Except for the south side, these walls are all partially below ground so some insulation is provided by the earth. If and when we build a deck, it is likely I will have more dirt added so that more of the basement is below ground and thus, better insulated. But we spend very little time in the basement during the winter so our only concern is to keep the pipes from freezing.

In contrast, the main floor is where we spend almost all our time. Since heat rises, this works out good during the winter. I discovered that our 1952 brick rancher has 2.5 inch thick batt insulation with black backing. It is orangey in color and appears to be fiberglass. According to Foam It Green, this insulation is R-8.75. Insulation is measured in R-values. The higher the R-value, the better your walls and roof will resist the transfer of heat. The United States Department of Energy "Energy Savers Booklet" (a broken link as of 2017) says that homes in the Maryland area should have R13-R15 insulation. This means that our walls have 62.5% of the recommended level of insulation. Obviously, this isn't ideal but it is certainly better than nothing. Given that our wall frames are made using 2x4s, I don't see how we could improve on this in a cost effective manner.

On February 22, 2010, I had a Baltimore Gas and Electric (BGE) Quick Home Energy Check-Up performed by Elysian Energy. The cost was free. While I didn't necessarily learn too much that I didn't already know, it was good to have someone with a trained eye point out things I'd overlooked. For example, there were several places where our fiberglass batt insulation was crushed. Naturally, these spots were insulating very poorly. Also, cold air was coming in due to the top part of our front door not fitting properly. Similarly, cold air was coming from holes in the cinder block used as passage for our dryer vent and electrical wires. Our hot water heater was well insulated but the pipes that ran from it and the boiler were not. Several other things were mentioned, but these are the highlights.

I took several notes that day and eventually made sure that all items of concern were taken care of. This is really a good service that BGE provides and I applaud them. I only wish more people would take advantage of it.

During the winter, we turn our upstairs thermostat down to 60 degrees. We don't have central air so in the summer, we use a whole house fan or window air conditioning units. On a hot summer night, we close the bedroom door and only run the air conditioner to cool that one room.

As the weather turns cold, Norma puts plastic window coverings on the windows. This helps keep the windows from transferring heat and cold. That is when I learned that our upstairs bathroom window has a leak. I'm not talking about a leak between the double panes, but rather an actual gap between the two windows that slide up and down. How did I discover this? After I saw three stink bugs between the glass and the plastic window coverings. I know they weren't there when the coverings were first installed. I'll be looking into this soon.

All these things helped reduce our energy costs. But our energy bills were still much higher than we wanted. With most of our low budget options exhausted, we looked towards more expensive alternatives that would pay for themselves quickly. My most costly energy saving investment to date was getting solar panels installed. That should pay for itself in about 5 years, assuming energy costs remaining what they were at the time of purchase.

We also considered replacing an old (not sure how old since it was free) 12 cubic foot upright freezer. In mid-September 2010, I did a 25 hour study using an energy meter to determine that this appliance consumes approximately 1034 kilowatt hours (kWh) per year. By contrast, an Energy Star rated Whirlpool White 16.0 cu. ft. Upright Freezer uses 409 kWh per year and costs $636 after tax while an Energy Star rated Kenmore White 13 cu. ft. Chest Freezer uses 326 kWh per year and costs $425 after tax (or $356.16 after tax during a Sears Kenmore sale). Note that shipping is not included in these costs but in-store pick-up is often available. I later learned that this "supposedly" big discount from Sears is only if you buy 4 appliances over $399.

On April 6, 2011, I ended up buying the Frigidaire 14.9 cu. ft. Chest Freezer from Lowe's. After tax, it came out to $386.53. There was a 15% off sale. I also got free shipping. This appliance uses 357 kWh per year.

This means that at $0.0919 per kWh (Dominion's February 2011 rate), we save $62.22 per year ($5.19 per month) by replacing our old freezer. I then took advantage of BGE's refrigerator/freezer recycling program which pays $50 to take our old working freezer. I tried to get another $50 since we are purchasing one with an energy star rating but this offer only applies for refrigerators and clothes washers. This means that our new freezer will pay for itself in 5.4 years (by September 2016). Of course, once it pays for itself, it is like getting an additional $62.22 per year for doing nothing...and having more freezer space too!

Another not-so-low budget energy saving option is adding insulation to the attic. According to the "Energy Savers Booklet",
     only 20% of homes built before 1980 are well insulated
     one of the most cost-effective ways to make your home more comfortable year-round is to add insulation to your attic.

For zone 4 (where we live), it is recommended to have between R38 and R60 insulation. When we bought the house, R13 fiberglass batt insulation was in the attic...much of it under the 5 inch space between 2x6 boards that run the width of the attic. Pressboard lies on top of this so the attic space can be used for storage. To bring us up-to-par, we need to almost triple the amount of existing insulation! Not an easy task, but one we are up to.

Raising the floor

Our house has 1592 square feet of living space. This isn't much, so it is important to maximize all the storage space we have. Boards in the central portion of the 24x36 foot attic provide about 500 square feet of usable space, though much of is under a low ceiling. If we simply add in enough insulation to give the attic an R38 rating, then we lose this much coveted storage area. Thus, I first planned to raise the center of the attic floor by 11 inches. This would retain much of the storage area AND give us additional insulation which would rest below and around the floor.

The original attic floor is comprised of 2x6 boards, place on edge, that run from east to west (the short side). To raise the floor, I used several 2x10 boards, placed on edge, running north to south. This helps to minimize heat/cold transfer through the wood. I used medium twist strap 12 (MTS12) steel connectors to secure the new floor boards to the old ones. These were attached using 1.25 inch long coarse threaded drywall screws.

Next, I cut cross beams to give additional support and rigidity to the structure. These were attached using 3 inch long coarse threaded drywall screws.

Since we have a whole house fan, I had to make sure the new floor structure would allow the covering on top of the fan to open and keep insulation away from it.

I also had to keep insulation away from the single CE6 Housing D27L recessed light. To do this, I enclosed the light with wood, including a wooden covering. I was unable to find an "IL" marking indicating that it has an "insulation contact" rating but the salesperson at Home Depot told me that if it has a brushed nickle appearance, then it likely is. I turned on the light for several minutes and it hardly produced any heat. Still, I wanted to make sure nothing came in direct physical contact with it.

Speaking of lights, we also added bulb guards to protect us from bumping our heads on the light bulbs. With such a low ceiling, it would be easy to smash one's head into a bulb and get broken glass and mercury poisoning from the compact fluorescent lamp (CFL) bulbs. If you don't already have bulb guards in your attic with a low ceiling, I highly recommend them. At only $2.68 each plus tax, they are well worth the cost.

While cleaning up old bits of roofing material and broken floorboards, we found pieces from a child's puzzle and a domino. I also found pieces of newspaper dated from October 31, 1953!

Having finished the frame to support the raised floor (see photo), we were ready to deal with the insulation.


One of the most important but often overlooked part of adding insulation to an attic is ensuring proper ventilation. After all, it isn't just about keeping warm in the winter but also keeping cool in the summer and staying dry year-round. This is where rafter vents come in. They maintain a path from the soffit vents to the section of the attic above the insulation, thus maintaining good attic ventilation. Prior to our project, the rafter vents weren't as important since batt insulation (and not much of it) was used. But we would be applying blown-in insulation because it is cheaper and more effective at fitting to an uneven surface. Thus it would be better suited for applying directly above the existing fiberglass insulation.

Before adding rafter vents, we needed to locate the soffit vents. To do this, Norma crawled into the low parts of the attic while I climbed up one or two stories on a ladder to get directly under the soffit vents. With a 60 watt work light in one hand and a cell phone (to talk to Norma) in the other, I shined my light into the soffit vents and tapped on them. Norma followed the sound then looked for the light. About 4 out of 8 of the soffit vents were clogged so she couldn't see any light but she was able to hear my tapping and determine with reasonable certainty where the vents were located. Cleaning or replacing the soffit vents would be left for another day.

After Norma located the soffit vents and marked their positions in the attic, I crawled out to the edge of the attic then used a heavy duty stapler to attach each rafter vent under the roof. See first photo. With the rise of the roof being half the distance of the run, I was only able to generate enough force to operate the staple gun if lying on my back.

Our original plan was to use the old batt insulation as a wall to keep the blown-in insulation from getting down into the soffit area. Just using the rafter vents is not sufficient. But everything we read indicated that using boards would be better than batt. So we bought several one inch thick foam insulation boards then managed to get them home strapped to Norma's roof rack without breaking any...a major accomplishment in and of itself. Then we cut the boards into one foot wide and 8 foot long sections using a razor. I used more MTS12 connectors fastened to the roof rafters to secure the foam boards around the edges of the attic. This was very difficult since I had to crawl into the lowest sections of the attic then lie on my back surrounded by fiberglass insulation while I secured 1.25 inch long drywall screws into the rafters.

Working in fiberglass is not fun. But wearing thick clothing and a breathing mask makes the task much easier. Still, after all the crawling, a significant amount of fiberglass managed to make it through my clothes and onto my butt cheeks. So I had an itchy ass for a few days. Fortunately, my hands didn't seem bothered which was good since I found it too difficult to work while wearing gloves. But the breathing mask was the most essential item. Without it, we would cough almost until we gagged. I don't know if it was the fiberglass dust, the dust that accumulated over the last 59 years, or a combination of the two. I just know it wasn't healthy to be inhaling that stuff. I tried wearing goggles but they got steamed up so I just did without. My eyes didn't feel so good but after a day, they were fine. Without a doubt, the most important thing was the breathing mask. After that, I would say knee pads. See second photo.

With all the prep work done, the next step was to blow in the insulation. We considered two options: GreenFiber and the Atticat Blown-In Insulation System. At first, I was more inclined to using GreenFiber for environmental reasons. But then I started thinking about the things that are more environmentally friendly but less effective:

  • Some cleaning product whose name I forget. Maybe they went out of business because it wasn't very good. It left streaks on stuff. Spend more money and get an inferior product, all in the name of saving the environment, which I was starting to question...was it really just for marketing?
  • Battery powered lawn mower: Fine if you have a postage-sized lot but with six tenths of an acre, it took several charges over multiple days to mow.
  • Tankless water heater: Fine if you like a moderately warm shower. It's a good idea but as of 2008, it can use some improving.

  • So maybe GreenFiber uses less energy to create and is made of 85% recycled material. At $9.78 per bag at Home Depot, it is the less expensive choice. I read the bag and noticed that when it came to mold resistance, it was given an "adequate" rating. I did some on-line reading and found a few postings that claim the cellulose insulation is less mold resistant. One person even wrote the following:
    As a mold remediator, I can tell you that Cellulose Insulation makes excellent mold food. In fact, I'll be removing some contaminated insulation next week!
    Of course, anyone can post anything they want but when I read similar statements from multiple sources, I started to wonder. Folks who bought this product usually gave it very high ratings although that is generally the initial reaction. The question is how it performs even after several years. Some of the employees at Home Depot spoke much more highly of the fiberglass blown-in insulation, claiming it was easier to work with and produced less dust. In terms of cost, the fiberglass blown-in wasn't that much more expensive. As much as I'd love to help out the environment by buying a product made out of recycled material, I know I'll be stuck with whatever I use for several years, and adding insulation to an attic isn't something I want to do more than once for a house. So we decided to go with the Atticat Blown-In Insulation System.

    We rented a truck at Home Depot to get the Atticat insulation blower and several bags of insulation home. The Columbia store doesn't seem to have much in terms of rentals while the Ellicott City store has a lot and the Catonsville store also has a good bit though maybe not as much.

    It was no problem moving the Atticat with two people. Setting it up was a breeze. Just connect the hoses and plug it in. Very simple and easy to use.

    Working with Atticat insulation, made by Owens Corning, was a pleasure. Let me rephrase was downright fun! Norma pushed the bales of fiberglass into the AttiCat while I manned the 100 foot long hose in the attic. Feeding the insulation into the machine was easy and spraying it out into the attic brought out the kid in me. I felt like I was spraying cotton candy into the air. Very little dust was produced...almost none. After I got the hang of it, it was easy to control. I don't think I got much insulation where it wasn't supposed to go though I didn't always put it exactly where I wanted either. Not only was this task enjoyable, but it was fast too. If you get all your prep work done, you can easily blow in all the insulation you need (even for a large attic) in a half day.

    One nice thing about the Atticat is that it can be broken into two parts, which fit very nicely in my 2008 Subaru Impreza. So we didn't have to rent a truck to return it, though we did need it to avoid multiple trips when hauling the insulation home.

    The next step was replacing the floor boards. I fit them as best I could and for the spots I couldn't fit with existing boards, I cut them to fit. They were then secured with 1.5 inch long coarse threaded drywall screws.

    I made sure the insulation was evenly distributed and level. Then I did some cleaning. After a total of about 42 man-hours spread out over 2 weekends, we were done! See third and fourth photos.

    We started with an attic having R13 insulation. By the time we were done, we had added R35 insulation, thereby bringing our attic up to R48.


    25 pound bucket of 1.25 inch long coarse threaded drywall screws: $49.74. I should have bought a couple of large boxes. I'm guessing that I only used about 4 pounds.

    Big box of 3 inch long coarse threaded drywall screws: $19.97

    MTS12 braces to attach things at right angles on top of each other: 121 at $0.96 each = $116.16

    8 foot long 2x10 boards: 16 at $7.52 each = $195.44. 8 feet was the maximum length for getting into the attic.

    12 foot long 2x10 boards: 2 at $11.28 each = $22.56. Per foot, these were a little cheaper than the 8 foot long boards so I cut these to create the cross beams for the floor frame.

    1 inch thick 4x8 foot foam boards: 8 at $9.38 = $75.04

    Rafter vents: 8 at $1.88 = $15.04

    Bulb guards: 2 at $2.68 = $5.36

    Owens Corning L38Z PINK Fiberglass Loosefill Insulation for AttiCat: 12 bags at $28.97 each = $347.64

    AttiCat 24 hour rental: free with purchase of 10 bags of insulation

    Truck rental $19 for the first hour and $10 for each hour after: $20.52

    Fuel for truck rental: about $10

    Total, including sales tax: $928.53


    I mentioned earlier that our attic does not have the best ventilation. Air flows in through soffit vents and out through an opening in the roof where a fan resides. Back when this house was built, this amount of air flow might have been deemed sufficient but by modern standards, that is no longer the case.

    The roof fan is temperature-controlled. That is, when it gets hot, it turns on to help push hot air out. I can adjust the temperature setting. This works just fine assuming there is enough cool air that can flow into the attic. When it isn't on, stink bugs can enter the attic. So in 2011, I added a screen to keep these critters out.

    In January and February 2013, I added more soffit vent to increase the airflow into the attic. I intended to do this in the summer of 2012 but some of the soffit had come loose and wasps were building their nests in that area. So I decided to wait until winter when they were dormant. This was a good idea since I found at least a dozen wasp nests under the soffit.

    I removed much of the old white aluminum soffit. Underneathe, I found painted white plywood. I believe the plywood was what originally came with the house and the aluminum soffit was added later. In the plywood, were 16"x7" screened vents that fit over 14"x6" holes. See first photo. There were 2 on each side of the house, providing a total of about 4.7 square feet of soffit ventilation. In actuality, it was much less since these screens hadn't been cleaned since they were first installed about 60 years ago. Debris made them even less effective.

    I removed these old screened vents. The screws holding them in had been painted over so it wasn't easy. Looking in, I observed there were 2"x4" horizontal beams on each side of the vents. There was 14" of space between these beams. At one end of each beam on one side was another diagonal beam that supported the roof. This made it a little hard to cut bigger openings in the plywood since I had to make sure not to cut the diagonal beams. To do this, I used my Black and Decker saber saw, pulling the blade mostly out when I got near the diagonal beams. This ensured I made a shallow cut. By the time I was done, each 14"x6" hole was replaced by two or three holes about 14"x18". See second photo. On the north side, I had two holes replacing each original opening while on the other sides, I had three holes. The north and south sides of the house are the short sides so not as much airflow is needed but our prevailing winds are from the north, so I wanted to make sure to got plenty of airflow from that side. Also, I didn't want to do any more work than necessary on the south side since that is the side where the power lines attach to the house. Working around that high voltage wasn't easy or fun.

    After cutting the holes, I covered them with screens. See third photo. Althogh the soffit vent openings are small enough to keep insects out, crafty critters like stink bugs might find their way around the sides so I figured the screen would make a good second barrier.

    Next, I used drywall screws to reinforce the plywood attachment to the horizontal beams. The plywood isn't in great shape but it only needs to support the weight of the screens and the soffit.

    Lastly, I cut and installed new white aluminum soffit and used it to replace the solid soffit in the places where I cut holes in the plywood. See fourth photo.

    I estimate that I spent about 28 hours on this project and $310 in materials to include soffit vent, screen, screws, and a $110 6-14 foot extension ladder. I already had a 6 foot A-frame ladder and a 24 foot extension ladder but for the north side of the house, I needed something in between to work safely.

    I now have 38.5 square feet of soffit airflow, which is at least 8.19 times more than I originally had!

    The lowest part of our roof covers about 1134 square feet.

    As a rule of thumb, one square ft. of vent opening is needed for every 150 square ft. of ceiling.
    - from Insulation - CertainTeed Learning Center

    This means that our house needs 7.56 square feet of ventilation. We now have over 5 times that much! But prior to this work, our ventilation was insufficient.

    Additional work

    Our attic will never be a finished or pretty area. All we want is an energy efficient, well-insulated, ventilated, clean, dry, safe area that can be used for storage. Since our total storage space is less than what is was, we need to be a little clever in how things are arranged. Norma suggested storing things like screens in an upright manner so that they don't take up so much floor surface area. This will also prevent insulation from blowing around every time they fall down and create a wind.

    What's next? The attic is well insulated and there is plenty of air flow coming in. But we can stand to improve the airflow going out. Once we get a new roof, I plan to have a ridge vent installed at the top of the roof. Maybe I'll have our attic fan replaced by a solar-powered attic fan. I don't much like spending money on electricity if I don't have to.

    Adding insulation to the attic is our biggest project to date. After having completed such a huge task, we felt a great sense of accomplishment.

    Physically, this job was very demanding. Lots of crawling around. My hips and upper legs were quite sore. Even 3 days after completing the job, I had a hard time running without cramping. So be sure to give yourself plenty of rest deserve it.