GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Insulating and Air-Sealing a Leaky Home: The Role of Windows

evan4 | Posted in General Questions on

First time posting here at the advice of an architect in our family. I recently moved into 2800 sq foot (above grade) home. There’s an additional 450 sq foot walkout basement and 500 sq foot unfinished (but conditioned) basement. So, almost 4000 sq feet including partial/below grade. The house was built in 1983. Our first winter was absolutely miserable. We have oil heat and usage was off the charts. In a 35 day period through January burned 360 gallons of oil and that was keeping average temps 68-70 degrees (we have a newborn so could not go much lower).

The most problematic room is our family room which is over a two car garage (photo attached). The room has a half vaulted ceiling (17′) and LOTS of glass. There are 5 windows in that room and two of them are 94″x54″. The room is also cantilevered over the garage by about 24-30 inches. The room is supplied by two ducts that cross through the garage and traverse through the cantilevered portion. The ducts delivery air at a lower velocity from others in the house and about 10 degrees cooler than other ducts. The room is also leads into a sunroom with even more leaky glass!

All of the windows in the house are original, *aluminum frame sliding glass*. To say they are drafty is an understatement. We have LOTS of large windows and glass slider doors. The window frame surface temperature is as low as 40 degrees throughout winter.

We had multiple energy audits with the caveat being, each of these companies has a hand in the game as they are insulation / hvac contractors. Hard to trust when they are also selling me the solution. Blower door test revealed 3800cfm and am told target is to get down to 2700 or so. I bought my own thermal imaging camera to do some air sealing on my own.

Every energy auditor told me “windows won’t make much of a difference.” I have a firm understanding of stack effect and the importance of air sealing and insulation. I find it hard to believe though that these windows are not drastically hurting our situation. Proof being, our master bedroom is the only room in house with newer windows and it is also the most comfortable room in the house.

The attic has original fiberglass batts R-30 on the floor. Pretty sloppy distribution and quite filthy. We have recessed lights throughout the house so lots of opportunity for leaks. Our HVAC unit is in the attic (also one in basement). We are in Zone 4, Northern Westchester County NY

I’ve had two different approaches proposed to me for solving our problems.

1. Remove all existing insulation in attic. Seal all penetrations. Blown in cellulose in attic to R49. Air seal penetrations in garage and dense pack garage ceiling. Dense pack cantilever. Spray foam accessible rim joists. Approximate cost 15-16k

2. Remove all existing insulation in attic. Open cell spray foam on roof rafters to R38. Open cell spray foam to attic wall to R-21. Spray foam to garage ceiling R30 (cut channels to apply). Spray foam R21 to rafters of cantilevered portion above garage. R21 sprayed on sill plates in basement. Approximate cost 17-18k

I think I need to also pursue the windows unless someone can convince me that the insulation and air sealing will improve things so drastically that I can keep the windows!

Sorry for the long post. Just looking for some guidance and want to make the best decision. Thanks for any help!

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    NICK KEENAN | | #1

    You're on the right track and asking good questions. I like that your emphasis is on comfort, often that's a better metric than trying to calculate payback periods. It's good that you had a blower door done, air sealing is the first thing to check. If I'm reading your numbers right, you got 3800 cfm. With 4000 square feet and an average ceiling height of 8' you'd have 32,000 cubic feet of house volume, or about 8.4 minutes to do an air change which gives sightly over 7 air changes per hour (ACH). That's actually not terrible, especially for a house of that age. Getting it down to 2700 gets you to 5 ACH. You may want to go even lower, 3 is code now and a lot of posters here get below 1. Getting your house air tight makes it more comfortable, less drafty, quieter and less dusty. The only downside is if you get too tight you have to think about mechanical ventilation to clear out humidity and CO2.

    Rather than answering your question directly, I recommend you make an energy model of the house. The process involves a combination of measuring and guessing the attributes of your house and putting them into modeling software. Then you compare actual energy usage -- which you have -- against the model, and adjust your guesses until actual usage squares with the model.

    Then you can put different suggested improvements into the model and see how they affect the modeled usage. You'll be able to see for yourself where to put your money.

    1. evan4 | | #10

      My apologies for the very delayed reply. I posted this and with my newborn and the house, had no time to get on here and respond thoughtfully. I appreciate your input. Regarding the energy modeling, while it sounds useful, would my approach of tackling the insulation/air sealing and windows little by little also work? I guess my big question to summarize is is foam in attic vs cellulose and then second question is the importance of window replacement.

      The way I see it, room over the garage is terribly cold and has lots of leaky glass. Floor/garage is inadequately insulated and definitely not sealed. Short of increasing heat supply to the room (which would be inefficient as the heat will not be retained), I can’t think of another way to mitigate. As you picked up on, While cost is a factor, comfort is paramount. We just moved here and plan to live here indefinitely. We need to be comfortable for the next X number of years. Also, with the way our oil bills are, a bit of improvement would certainly help.

      Speaking more with insulation contractor, if I go with foam in the attic, the question now is what R-value to go with. The options presented to me are R-30, R-39, R-49 on the attic ceiling. In my area, r-49 is code. Obviously higher we go, higher the cost goes. Is it advisable to go to full r-49? Adds about 2k-3k to the cost from r-30.

      Thank you!

      1. Danan_S | | #21

        Following up on what DCContrarian said that to really solve the problem, you need to understand how the house works as a system, which is what modeling will demonstrate. Remember, heat follows the path of least resistance, so if you stop one leak, it can just end up sending more air through another one. You can probably make some areas more comfortable with localized measures, but the energy consumption of the house won't change much unless you the address the issue holistically.

        > The most problematic room is our family room which is over a two car garage (photo attached).

        Rooms over garages, when not fully sealed off from the garages, can be a big air quality problem, especially considering you have a newborn. Think of the fumes coming out of a hot ICE car engine right after you park it, or the off-gassing from the chemicals people often store in garages. If it were me, before I addressed any energy issues, I'd do my best to seal off that garage from any adjacent living spaces with air quality as the primary goal, not energy efficiency.

        If you start tightening up the attic and roof of house without addressing the garage first, you could end up trapping whatever comes out of the garage in the house. You might hate the leaks in your house right now, but they are probably helping to dissipate that stuff.

        > Proof being, our master bedroom is the only room in house with newer windows and it is also the most comfortable room in the house.

        I'd be careful about jumping to a 1 dimensional conclusion like that. It could also be that it gets more sun, has shorter or better insulated duct runs, has fewer exterior walls, and could just be a smaller space so more easily heated. Sure, windows might be a factor, but considering how many other energy/comfort problems are going on in the house, the causes are probably many.

      2. Expert Member
        NICK KEENAN | | #23

        Here's the thing: insulating and weatherizing is always about cost/benefit. The reason modeling is important is that you can't trust your senses to tell you what's happening. Just because a room is cold and drafty doesn't mean it's inefficient, and more crucially, just because a room is comfortable doesn't mean it's efficient. The more comfortable room could just be better heated, and could actually be losing more energy and thus have the best cost/benefit ratio for improvements

        Now, the alternative to modeling is to look at actual performance; in fact you should look at both together for the fullest picture. Performance of the entire house comes from your monthly fuel bill. Room-by-room performance is a little trickier, you have to look at how your system was designed and whether it's functioning as designed. You can start with things like counting the number and size of heating ducts.

  2. Expert Member
    NICK KEENAN | | #2

    In a 35 day period through January burned 360 gallons of oil and that was keeping average temps 68-70 degrees (we have a newborn so could not go much lower).

    An off-topic comment about this: your pediatrician should have talked to you about Sudden Infant Death Syndrome (SIDS). It happens most commonly in the winter and is strongly correlated with infants sleeping in heated rooms. To reduce the risk an infant's bedroom should be kept in the low to mid sixties.

    1. brianvarick | | #5

      Where are you seeing that recommended?

    2. evan4 | | #11

      This is actually not at all true. American academy of pediatrics recommends 68-72. Low 60’s is cold, especially for newborns.

  3. Expert Member
    Akos | | #3

    Without moving the air handler out of the attic, you'll always have a huge energy leak in your house unless you spray foam the attic. Looking at the cost difference, I would go for spray foam. This way you can also use your attic as storage space provided your joists are rated for the weight. Keep in mind that a spray foam attic needs to be conditioned, so make sure there is a supply vent up there.

    An in-between would be to spray foam encapsulate the ducting and build a small insulated doghouse for the air handler. Loose fill the attic and dense pack the rest of the house. This reduces the amount of foam plus dense pack does a pretty good job air sealing and a friendlier to your wallet and environment.

    Your energy consultant is correct about the older double pane aluminum sliders. They are much better than older single panes but not much worse than newer budget double pane windows.

    They can leak a lot of air which does create comfort issues which sounds like the issue you are having. I would replace any larger ones in the living space with better sealed units.

    1. evan4 | | #12

      Apologies for my late reply. Appreciate your input. Regarding your comment on windows, I think that will be our approach: replace the larger windows in the most problematics rooms. The current windows, while they are double pane, the metal frames are incredibly cold and drafty. Previous owners replaced the glass in all the windows. My guess is the panes had bad seals and glass was hazy. They planned on selling and did this as a prep to flip the house. They installed the cheapest, most basic glass. Not low E or anything insulating. In addition to the cold winter days, now that it’s warming up, an day that is sunny and 72-73 degs or warmer, the house shoots up to 82-83 degrees in no time. Probably a combination of the glass and poorly insulated attic?

  4. Deleted | | #4


  5. plumb_bob | | #6

    CCSF is over prescribed and not the best solution for many situations, but I would guess that this is a situation where it may be the best choice. I would vote for option #2, but with closed cell foam.

    A note about a poorly sealed living space above a garage- the potential for home air quality to be negatively effected by vehicle exhaust is high, and it can be dangerous. Make sure you have a CO detector.

    1. evan4 | | #13

      Sorry for delay. The closed cell foam is cost prohibitive at this time in my area. Additionally I have concerns about if there were ever a roof leak, we would not spot the leak for very long time. We have lots of co detectors and appreciate your concern for the co! That is one of my great concerns as well!

  6. user-6623302 | | #7

    Have you had the heating system checked for proper function? Fan speeds correct and working? Filters all clean? Water temperature at design? Outdoor reset working and curve is correct? Not using setbacks? Could you have a oil leak? Is the oil tank buried or any of the lines?

    Windows, the seals and weather stripping are most likely shot. I bet new material could be obtained to rehab the moving panels and the jams.

    There is plenty of info on this site about how to deal with the cold room over the garage, "bonus room" issues.

    What is the insulation situation with that vaulted ceiling? Have you considered adding the insulation to the outside of the roof?

    I would replace all of the can lights with new LED sealed lights, air seals and reduces electric use.

    While you use a lot of oil, given the size of your house, it is high but no out of sight. Are you using oil to make your hot water? That could be 20-30 gallons of oil a month. You may look hear for some savings. Maybe a hybrid water heater.

  7. nynick | | #8

    I'm in Northern Westchester as well. Been there since 1980. If I were you, I'd spend my time chasing leaks and drafts first before adding insulation here and there. Lightly pressurize your house with a home made blower door (a fan and some plastic) and spend a few hours with a smoke pencil and some stickies marking the areas that need to be sealed or weatherstripped. I'm betting you can go a long way to help your comfort levels with this approach first....and it's cheap to do. After that you can determine how much added insulation you may need.

    Bonus rooms and rooms over garages are notoriously chilly. More times than not the garage ceiling/bonus room floor isn't insulated. A small hole poked in your garage ceiling will tell you whether it is or isn't. If not and the drywall as to come down...big job but can be DIY. And check for drafts here too.

    As an aside, I've been burning wood in an airtight wood stove for 40 years. Raised all 3 kids while doing so. Almost all that wood came from the trees on the property that either needed to come down or came down by themselves. Probably not the most politically correct thing to talk about on this forum, but there you have it.

    1. evan4 | | #15

      Thanks NYNick. I’ve done a lot of air sealing over the last few months! Still going and the bigger part of that project (garage) I will leave to a contractor :) I found a number of holes in the house (I.e. abandoned dryer vents). That were never properly sealed, or sealed up at all! What is wrong with people?!

    2. agm413 | | #19

      > not and the drywall as to come down...big job but can be DIY. And check for drafts here too.

      You can also just cut holes in the ceiling or rim joists/perpendicular joist bays and do blown in. Cheaper and easier than bringing down a whole x rated ceiling.

      1. evan4 | | #24

        So you would advocate blown in cellulose over foam in this case of my garage ceiling?

    3. Danan_S | | #22

      > I've been burning wood in an airtight wood stove for 40 years. Probably not the most politically correct thing to talk about on this forum, but there you have it.

      Does this forum have a problem with wood burning for heat when used in the right context? If you are in an area where particulate pollution isn't an issue (i.e. sparsely populated wooded areas), then burning wood in a high efficiency stove seems like a carbon-neutral way to heat - far better from a "green" perspective in nearly every way than burning fossil fuels like heating oil or natural gas.

  8. Expert Member
    PETER G ENGLE PE | | #9

    Option #2 is a non-starter, as open-cell spray foam in an uninsulated roof system is not acceptable for cold climates. Open cell is too vapor-open and you will get condensation against the roof sheathing. Installation of a smart vapor retarder membrane can solve this issue, but installing one as a retrofit inside an attic is unlikely to be successful. Also, you should be aiming for something near current code compliance, which is R-60 in cold climates. Depending on your ductwork location and routing, you may be able to use closed-cell spray foam to seal the ductwork and then bury it in loose-fill cellulose. While it can be difficult to properly air-seal the HVAC equipment itself, it is easier than the whole duct network. I have done jobs similar to option #1 with good success. Also, you have 30%-50% more surface area being insulated in option #2 - that equates to an equally large heat loss in addition to the underperforming R-38 insulation.

    I would probably go for option #1, with blower door directed air sealing elsewhere. New windows rarely pay for themselves in heat savings, but they can add value through improved comfort, operability, and aesthetics.

    1. evan4 | | #16

      Peter, thank you for this input. Why is there so much divide on open cell? Every contractor that stepped foot in here has offered open cell. I even know a number of people who had it installed in my area. Closed cell is cost prohibitive for me so that’s not an option. Doesn’t open cell allow vapor to pass through? And wouldn’t this minimize moisture on roof sheathing? I think I’m not understanding that part well enough.

      1. user-2310254 | | #29


        Unfortunately, you have to be cautious about accepting advice from contractors. I suspect they are suggesting open cell because it is the most cost-competitive material they have to offer. For more on why open cell in cold climates is a bad idea, see this article:

  9. evan4 | | #14

    My apologies for delayed response.

    Yes, heating system has been checked by two hvac companies at this point. It is a single speed unit so no adjustment to fan speed is possible. Oil tank is above ground, in my basement and not leaking.

    All of the recessed lights are brand new Halo sealed units. While they showed a slight leak during blower door test (2-3 degs difference), under normal conditions without blower, I get a 1-2 deg difference from ambient temp and light temp. Not certain if this is significant but if I understand correct, it’s not too significant.

    Hot water heater is running off oil as well (from oil burner). Agreed, this is not efficient as I hear it kick on now throughout the day despite heat being off. I cring at the cost each time it fires up! The hot water tank is 11 years old and I’ll look at replacement options soon. It is interesting that you say my states oil usage is not far off for a house this size. In speaking with people, it seems my oil usage is 30-40% more than people in my area with comparable houses get. The energy auditors also felt it was pretty high usage. I will add, despite the high consumption of oil we are not even close to comfortable. The house is still way too cold for comfort and the burner is firing up constantly.

    Vaulted ceilings insulation is unknown. It’s definitely insulated but we don’t know how well. The roof is fairly new and I have not considered insulating from the outside. This option also was not presented to me by anyone.

  10. PBP1 | | #17

    Is the garage ceiling drywalled? Maybe obvious, though, if exposed, you may want to consider DIY spray foam (kit or cans) and insulation (batts or boards), followed by drywall and taping/painting - and maybe see if you can access the overhang bays that extend past the garage wall. All of those are pretty easy DIY projects with readily available items - total DIY cost may be under $2K.

    The high ceilings, windows, above garage placement of that family room is a bad mix for stack drafts and stratification (depending on time of year, heating, cooling, etc.). For sure you don't want vehicle fumes streaming through or fumes from whatever else may be in the garage.

    I had my garage ceiling spray foamed (closed cell) along with batts (flash-n-batt) and then drywalled, taped and painted. The floor of the room above the garage is very comfy.

    I used an energy consultant/HERS rater as a HERS rating was required by the city. HVAC, insulators and energy consultant worked together just fine. In the years since my house was finished, I've hunted down some leaks and sealed, which has improved comfort beyond what was already quite comfortable, noting important to monitor things like CO2.

  11. oberon476 | | #18

    "I think I need to also pursue the windows unless someone can convince me that the insulation and air sealing will improve things so drastically that I can keep the windows!"

    It's common for people who are upgrading an older home to look first at the windows, and if they are single pane in terrible shape that makes sense, but in your case even though you can do a lot better than what you have, the windows should be about the last thing that you address when improving your homes energy performance. Too many people blow their budget on new windows and then have to skimp on the more important (for energy performance) improvements

    Air sealing and improved insulation will get you more bang for your bucks than will installing new windows. Not saying don't do it, just saying make it a lower priority if improved energy performance is your motivation.

  12. walta100 | | #20

    Consider this house is an energy and comfort nightmare fixing that will cost lots of money that will not increase homes resale value in the slightest, the smart move maybe to sell it as it is and buy something better from an energy point of view. There are no cheap and easy fixes for the house you have described. The fixes for the HVAC, windows and insulation may recover their costs but pay back is likely to be 30+ years.

    If you are determined to stay, as someone that lived thru winters with 70s aluminum windows, I say replace the windows before the next winter. My guess is the people that say window replacement is a poor economic choice never got up to find the window frame covered in ice an inch thick. I agree not to replace old wood and vinyl windows but steel and aluminum I say change for comfort if for no other reason.

    If you are determined to stay, I would have the duct work tested and sealed with a “Duct Blaster” and burry the duct work deeply in cheap fluffy insulation. Note this is a risky plan if you live in a hot and humid climate maybe not so much in NY.


  13. user-1072251 | | #25

    At 7 ACH50, your house is built leaky. If the windows ice up on the interior, definitely replace them because they are huge thermal bridge, carrying your heat outdoors. otherwise concentrate first on thorough air sealing before dealing with insulation. Often, the air you feel around windows is due to poor insulating around the windows, not the windows themselves. The typical issue with a garage under is they are poorly air sealed, so it might be a major re-do project. I’d suggest you try for 2 ACH50; might be hard to reach, but you will notice the difference in comfort and heating. Sills - between the concrete and wood are often huge air leaks. If you have any spaces where the drywall covers concrete and the sill, it’ll be worth cutting it away to seal the sill. (Spray foam is best there). Garage doors are also terrible, but that simply argues for better air sealing. Once your house is tight, then the insulation will help keep that heat inside the house. The issue with open cell spray foam is that it’s moisture permeable (water vapor passes through). On the interior of the roof sheathing, that moisture will condense on the sheathing; the foam will delay drying, and the roof can rot. Not good. CCSF is impermeable so moisture does not pass through. If you use it because it’s cheaper, wait til you have to replace your roof. Ideally with fiberous insulation, we leave an air channel against the sheathing with soffit vents and ridge vents. Your house will be a challenge but it is doable.

    One problem is intermediate testing which is very helpful. I did one large room in my house by a DIY “blower door” by taping the door, and putting a box fan in the window (blowing out) surrounded by cardboard and painters tape - so I could easily find and fix the leaks. It made a huge difference. Good luck! After insulating our basement (a huge help) we tossed the oil, and propane and stopped using the wood stove and installed mini splits. Comfortable all the time now.

    1. evan4 | | #26

      Thanks for all that. When you speak of fibrous insulation, are you referring to material such as blown cellulose? And would you advocate for that over spray foam?

  14. user-5946022 | | #27

    If closed cell spray foam (CCSP) is ruled out due to affordability, then your only other consideration should be blown cellulose. As others have pointed out, Open Cell Spray Foam in a cold climate can rot your roof and cause a far more expensive issue.

    The nice thing about spray foams is they air seal and insulate. While blown cellulose does block air better than fiberglass, it does not inherently air seal. Someone will need to air seal the house before the cellulose is installed. It is difficult to get people to properly air seal.

    The biggest problem with all of this is if you pay people for a fix and don't get the intended results. You need some sort of performance measure. Typically, blower door results are measured in ACH (Air Changes per Hour)/50 pascals. If your house is currently blowing an 8, decide what you want to pay for, and require the contractors to agree to getting the house to a 4 or a 3 or whatever. The starting and ending blower door tests should be done by an independent company - not the contractor who does the air sealing.

    If you do decide to replace windows, use the opportunity to redo the insulation around the windows. I suspect the above posters are correct about that being minimal. Also remember that it is NOT just about the window itself - how the window is installed makes just as much impact as the quality of the window. Consider tackling one room or one area so that you can confirm window replacement increased comfort.

    By the way - that pic shows a very nice home. Congrats on that and the new baby.

  15. Robert Opaluch | | #28

    When recommending closed cell spray foam, it should be noted there is a risk, besides the negatives of high cost and environmental negatives. Site applied spray foam is done by professionals who wear a hazmat suit with a fresh air supply because the stuff is poisonous until well cured (24 to 72 hours). In some cases, it continuous to offgas, and the smell or chemical off gassing sickens those who have an "allergic reaction." Unfortunately, once applied (successfully or not so successfully) it is not possible to remove it all without removing material to which closed cell spray foam sticks tenaciously. And disposing of it is a problem eventually, its not recyclable like some other insulation alternatives. Factory-manufactured rigid foam boards avoid most of these problems.

    We keep seeing Q&A's about fumes and removal of closed cell spray foam, which is tragic. Search them to see the problems people can experience. Yes closed cell spray foam has air sealing and high R-value advantages. But cost, health risk, environmental damage and disposal issues should be noted for a balanced view. Alternative insulation products like blown cellulose, dense packed cellulose, fiberglass batts or loose fill, mineral wool batts, semi-rigid board and loose fill, and factory manufactured foam board products (EPS, GPS, polyiso) seem more cost-effective and less risky.

    No one has mentioned mineral wool batts that are more expensive than fiberglass batts, but fill stud bays well and offer a higher R-value. Cellulose is a more affordable product for dense packed walls (if a contractor is available in your area), or you can blow cellulose in your attic areas yourself at low cost (after air sealing work is complete). These seem like the most DIY friendly choices.

  16. user-1072251 | | #30

    RE: Fiberous insulation:
    We stopped using fiberglass insulation years ago. (although it's still widely used and kind of works.) Our typical houses are all dense packed cellulose walls and cathedral ceilings, and open spray cellulose in a "flat" attic. Rock wool is excellent; especially for DIY work. Relative to cathedral ceilings, we've found that dense packing the bays can collapse the plastic or foam vent channels (leading to mold) so we install a 1-1/2" plywood (1/4") air channel and fill the remaining cavity with DP cellulose. We actually use very little CCSF - expensive and a very high carbon footprint, where the cellulose is the opposite - less expensive and low carbon footprint.
    In most cases we try for R60 roofs, which may involve making the rafter cavity deeper by suspending 2x4's from the rafters to create the desired depth. It's not very expensive or time consuming and works well.

    1. evan4 | | #31

      Thanks for that. Are you suggesting insulating rafters vs the attic floor?

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |