Insulating old house

Discussion in 'Remodel Forum & Blog' started by Master Brian, Jan 9, 2009.

  1. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    South of Boston, MA
    I've looked thru a couple sites on line
    R Value of single pane seems to be .85 up to 1.3 - very low
    Storm windows can save heat loss by 25 to 50%
    2x glaze w/argon are from R3 - 3.3
    3x glaze argon R6.2 - I have seen ratings up to R10
    I'm not sure how old these ratings are?

    From Energy Star site:
    I found this strange as my windows have paid for themselves in savings on my energy bill.

    One big advantage for me is the house is MUCH quieter

    I had one window that one pane was cracked
    2 windows that were fogged up
    2 windows that built in vinyl "lift" along the bottom edge was cracked & breaking
    I think they might have been 8-10 years old (vinyl in & out)
    I ended up replacing 15 windows in the house & 3 doors
    Last edited: Jan 13, 2009
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    Keep in mind that an old window probably also leaks air, disregarding the fact the single pane of glass is almost like an open window by itself. New windows would cut down air infiltration AND be better insulation. They also probably have some radiant barrier effects, that make it appear to be warmer.
  3. frenchie

    frenchie Jack of all trades

    Both true. The denser pack also cuts down on airflow a lot, which in my climate is a good thing - prevents warm vapor-laden air from inside leaking into the wall, condensing against back of the siding, making water.

    One the other big plus-es about cellullose is that it will store excess humidity, keeping the wood dry.

    The minus is that it will store excess humidity. So if you have leaks into the wall, it'll soak it up... not goog. Also, if it gets damp often enough, eventually, it will settle.

    I haven't used either one before, so this is all 2nd and 3rd hand.

    No advantage, compared to just filling the wall. Without the airspace behing the cladding, there's no drying mechanism. And moisture doesn't settle via gravity, the way bulk water does. If it did, your foam stop would also stop the moisture, re-directing it towards the inside...
  4. frenchie

    frenchie Jack of all trades

    On the windows side-topic... like with walls, our rating systems suck. In terms of real-world performance, the R-factor of the glass is WAY less important than air leakage around the sashes, and/or around the whole unit.
  5. frenchie

    frenchie Jack of all trades


    And please stick around. We could really use some building-science-cognizant people around here. I try to touch on the principles behind the specific advice, but I'm no expert on the theoretical side.

    I also tend to get bogged down in the specific task at hand, the nuts & bolts.

    We've been wrapped up in the minutia of insulating Brian's walls, and you're reminding us to view those tactics in context of the larger strategy, the overall goal; and to always start with the low-hanging fruit.

  6. Master Brian

    Master Brian DIY Senior Member

    Maybe I should re-state....I won't argue the new windows are more "efficient", I will argue they aren't worth upgrading to, in a turn of the century house with original windows in good condition.

    From this website The solar heat gain from a single pane window is 88% from a Low-E double 65-75%. Unless I am reading that incorrectly, that is not 1/2, that is not 25%, that is maybe 23% at best, with a 10% swing towards being 13%. It's 70% solar heat gain from a triple pane and 78% from a double pane.

    That 23% isn't going to directly influence 23% of my bill, it is going to represent 23% of that windows heat loss. I wouldn't possibly know how to calculate that, but I have heard about 30% of heat loss comes from windows. What does that mean? Does that mean that if I spend $100 to heat my home, if it didn't have windows it would cost $70? I doubt that is the case, but wouldn't the 23% figured earlier, be 23% of that 30%? If that is correct that # is now 6.9%. If I am figuring that somewhat correctly, wouldn't that mean that if I replaced every window, I would be 6.9% more energy efficient? ....and if the $100 p/m heating cost was correct, and $30 p/m went out the windows in heat loss, then upgrading would maybe save me $7 per month. That is only $84 per year. If the life expentancy of these new windows is 30 years, the the break even would be $2500-$5000 to replace about 38 windows. I'd love to know where to get 38 Low-e oversized windows installed for under $5000 with a 30 year guarantee.

    If I am wrong, please correct me....I am sure I am off somewhere and I really do want to see the "true" benefits of replacing the windows. Everyone says it, but no one has explained it! They just throw out energy efficient as the reason. I want cost effective. Sure I can go buy a $30k, 40mile per gallon hibred to save gas, or I can drive my paid for suburban which gets 14mpg and pay for gas fo 14yrs, which would be the break even. I highly doubt I'll be driving either of them in 14yrs!!!
    *side note, I just double read some stuff and the question popped into my head, is solar heat gain, good or bad? I would think the more solar heat gain would be good in the winter, as it would allow more of the sun's heat into the house! right/wrong? A single pain window without gas allows more solar heat gain. Of course that is bad in the summer, but heavy blinds can slow that down. Maybe I used the solar heat gain #'s above incorrectly in my calculations, but the numbers still shouldn't be far off....

    I also have heard argon looses it benefit after a few years and the National Association of Home Builders gave me the window life expentancy info on the new windows. I took the information about the 100yr + life span on old heart wood windows from an episode of this old house where they showed how to rebuild these old windows to make them operate like new.

    I'm sure it'll save some, but how much depends upon more factors than just replacing. You already said one window was cracked, that kills any efficiency at all, no different that a hole. Then you point out you have vinyl windows, which are 8-10 yrs old and they are cracking and breaking. National Home Builders says windows should last 15-30yrs, but you say after 8-10 they are cracking, which tells me any argon would probably be pretty much gone as well and most new windows don't make thier life expectancy. I'm sorry, but I don't want a band-aide solution, I want my house fixed right with windows/doors that will last. Only ones that I see which will last is my original windows and the website quoted above also says that a good storm window can save almost as much on energy as a replacement window at a fraction of the cost!

    Again, I am sorry, if I am offending anyone. I just am the type of person that likes to know why, I don't like to be told, "because I said so". I'm not arguing windows need to be figured into the equation, they do and in some cases, replacing the windows is the right move, but I don't think a blanket call to replace with newer windows makes sense. After all isn't energy efficiency really about saving money? I am trying to stay very open about this and appreciate any feedback or corrections in my thinking.

    Chessiec, I also do very much appreciate your input on the other things to look for.

    frenchie, thank for clarifing my mistake in the "baffle" idea. I wondered if it would work. I think my next step is to call central inspection and speak with an inspector to possibly see what they say as well as see if I can reach someone with the local Dept of Energy. Maybe they can tell me about cases locally. From what I gather the vapor barrier really is less important in my climate than in some. We aren't overtly rainy, dry, or humid we aren't on the extreme, extreme cold or heat sides, we just get a little of all of it.
  7. frenchie

    frenchie Jack of all trades

    I just want to note that not everybody is telling you to replace your windows.

    Like I said, in the real world, air leakage is more important than R-value (which doesn't take air leakage into account). Old windows, if the weatherstripping is in good shape, no leaks around the frame or the sashes, with storms installed as well... pretty much as good as new windows, IMO.

    Most of the heat loss, in either case, is infiltration, not radiation.
  8. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    South of Boston, MA
    We have more of a heating season here (maybe 4.5 months), so my aim was to save on heating oil
    The old windows were double pane, LOWE vinyl replacements
    They were designed with a vinyl "lift" edge along the bottom of the window pane. This is what was used to open the window, it was too thin & this is what was cracking - no effect on heat loss
    One pane was cracked on one window - but since there was still an air space better then single pain. Same with the 2 fogged windows - argon was gone - but still an air space. IMO these were very cheap replacement windows that were quickly installed to sell the house years ago

    I would say the greatest return was simply replacing 3 basement single pane windows & 1 badly sealing door. And insulating the sill plate. Total cost was less then $500 & brought my basement from 45-48 up to 58-63.

    For windows I go by R Value, single pane = R1, 2x pane = R3
    3x better insulating value, but as said if the window doesn't seal correctly at the sash & frame that Rvalue is worthless

    I spent all told maybe $4500 on 15 windows & doors
    My heating cost was cut in 1/2 - more if I heat with some wood.
    I save at a min 1.5 tanks of oil a year = ~400 g x $3.25g = $1300 a year. This is the 4th heating season - oil was $4g (now down to $2.25). I didn't know what I would save before I started. But so far I have saved approx $5300 in 4 years (end of this heating season). The past 2 years the heat was kept at 70 - new baby. This year we dropped it back down to 68 (same as 3rd year) - 1st 2 years we lived here was before replacing the windows

    So this is my approx true cost savings over 4 years
    It all depends upon your heating season & method. I expect oil prices to go back up. With the addition, sunroom, dormer of my Cape I now have a total of 48 windows, 11 doors (1 slider), & 15 skylights
    I can't imagine moving into a house & needing to replace that many windows

    The largest window in the house was 4x5 fixed glass & was $450
    The next largest was 44x48 double hung & was under $400
    The largest window in the addition is 5x7
    If you only spend $200 a month to heat your house it is probably not worth it to save $100 a month. Do you have cooling costs?

    At $300 (low) a window * 38 = 11,400 - say $12,000 / $400 year savings
    That's a 30 year payback

    One Apt I rented 4 tubes of caulking was all that was needed to reduce our heating bill due to air leaks
  9. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    South of Boston, MA
    Just to clarify the main reasons I replaced all the windows:

    Cheap replacement windows were installed, & the areas that held the sash weights were not insulated

    1 cracked pain & 2 fogged windows, plus the cracked thin vinyl lift

    Residing the whole house, so better to put the windows in 1st - rather then have to do it 5-10 years down the road

    We had the $$ to do it from the sale of 2 homes, no $$ out of pocket

    More light - I like windows. The new picture window in the main room made a big difference

    There is a whole look & style to a Craftsmen house
    I would be inclined to insulate the walls 1st, then worry about the windows. If insulating the walls means taking the siding off, then I would look very closely at the cost/look of new windows that would match the style of your house (then decide)

    As Frenchie said, its the cold air blowing in that will be the biggest problem. I had a bathroom fan vent that the outside damper was broken. You could feel a cold breeze coming in when the wind came from the East. If your windows are tight around the frame & sill then you are in pretty good shape. I don't have any grilles as I can't stand the "fake" grille look

    The picture window is the only window with a grille in our house - non removeable. It also has the smaller windows divided "in the glass", seems like each one is a seperate little window

  10. Master Brian

    Master Brian DIY Senior Member

    frenchie, maybe the "everyone" should have been in quotes! It just seems to be the 1st thing people recommend, couple that with about 1-2 siding, guttering, window reps coming by the house each month and it feels like everyone actually says that.

    Add to that a very good friend whom builds houses. We constantly go around and around about new vs. old houses. He thinks I'm crazy for wanting to live in my 1915 craftsman, I think he's crazy for wanting to move every 2-5 yrs into a new house.

    Dave, I totally understand your reasons. I have 1 window that most likely can't be salvaged, it was just neglected for too many yrs. I am going to try to see what I can do with some good epoxy, but am hopeful I can find an exact replacement for the sash(s) at a local architural salvage. You seem to have found good buys on your windows, but I'm willing to bet they are a more standard size than what I have. In my last house, I had to special order 6 (?) windows, because all that had been installed on an addition were storms and I spent about $250 per window and they were about half the size of my current windows. Judgeing from the blinds I've been buying the windows here will be special order as well, I can't seem to find a standard in anything. As soon as special order is stamped, the price seems to double.

    ....this just hit a nerve! I am serious though, if anyone can show me how I am financially better off, I'd go for it. I just see the hope of insulation being the best bet to save some $$. I know caulking, spray foam and window glazing are definately going to become my best friends or worst enemy's depending upon how one looks at it. I haven't even gotten started painting much past the front porch area and I've already used a case of caulk and several cans of foam.
  11. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    South of Boston, MA
    We looked at new houses, not our style....and the cookie cutter neighborhoods where most of the houses look the same. My friend has moved & is on his 3rd house in maybe 6 years - not for me

    I went thru Home Depot for Anderson windows. Then I found after that the windows for HD are a "lower grade" then thru other smaller suppliers. Not 100% sure this is true. I just bought a 38x53 Anderson double hung Anderson with screen & it was just over $300. I special ordered 2 other windows & they were only 4' tall & less $$. Special order (for me) for HD just means its a normal Anderson Window size, they just don't have it in stock. Someone also told me if I have to special order an Anderson thru HD that it will be a "normal" grade Andereson window - not one made specially for HD. Again, not sure if that is true

    Insulation makes a big difference & will probably get you the most bang for your buck right now
  12. Master Brian

    Master Brian DIY Senior Member

    I insalled an Anderson Storm door from HD after I bought the house and I will say that is one GREAT door! I love the fact, it could be keyed to my Schlage locks that are on the rest of the house and it has an awesome seal. It was special order, because all of my doors are 86 (I believe) vs. the standard 82" height nd it was about $500. To be honest, the seal is almost too good as my huge oak front door is very tough to close now. I say this, because I am impressed by what HD carried in this line. They tend to be where I do go for windows/doors.

    Now back to insulation....
  13. frenchie

    frenchie Jack of all trades

    Brian - I don't know if you lurked around JLC much, but I was just reading this thread, and thought of your windows decision:
    standard warning: blah, blah, blah... it's not safe to post there, they're mean to strangers.

    As usual, a lot of chaff with the wheat! But posts 15, 16, 23, 30, 32, and 37 are worth reading.
  14. jch

    jch Member

    I'd have to agree with frenchie.

    I'm in British Columbia, where there have been 10's of 1,000's of "leaky condos"--buildings/houses that were super-insulated without enough thought to dealing with water penetrating into the wall cavity. There were so many claims for rotting/moldy houses that the provincial home insurance corporation went bankrupt...

    CMHC (the Canadian Mortgage and Housing Corporation) has since launched a whole series of seminars to teach the construction industry here about the lessons learned in this fiasco and how to avoid repeating them.

    I took their 65 hour course a few years ago.

    Here are the main points that apply to Master Brian's situation:

    1) Old houses with large eave overhangs, proper exterior window sills, and hollow (uninsulated) walls seldom rot or go moldy.

    2) The biggest mover of water vapour into a wall cavity is via *air* movement vs. vapour diffusion through the surface of the wall itself. i.e. air leakage through a 1" x 1" gap (or, equivalently, a 1/16" x 16" gap say along a baseboard or window jam) will deposit several *pints* of water into a wall cavity during a heating season. A non-vapour barriered (but air-sealed) wall will only deposit a few ounces of water during that same time. Therefore a perfect air barrier (with absolutely no cracks/gaps around penetrations in the wall like windows and doors) will prevent rot/mold much more than putting poly on the inside surface of your walls.

    3) A hollow wall will disperse moisture during the dry season. The interior side of the cladding will effectively be at "room temperature" and will therefore give up the moisture quite quickly. The unrestricted convection air currents within the wall will then disperse moisture enough to avoid rot/mold.

    4) Convective air currents within a wall "pump" heat through the wall. The air adjacent to the warm surface warms up, rises within the wall, cycles over to the other side of the wall (the cool side), gives up its heat, sinks, and then moves back over to the warm side.

    5) Insulation works by stopping these convective air currents within a wall. Loose fill insulation (fibreglas batts, cellulose, open-cell foam) have enough air resistance to stop the weak convective air currents, but offer little resistance to wind- or stack-effect pressure differences. As frenchie said, they act as simply a dust filter (hence the black stuff you see on insulation batts whereever there are air leaks).

    6) Old houses rarely have a reliable air barrier. Spaces between clapboards. Spaces around window jams. Stucco butting up against wood which swells and contracts during the seasons.

    7) Because we know that *air movement* transports the majority of moisture into old walls, we need to ensure that there is a mechanism to get that moisture out of the wall before rot/mold sets in. In old houses, the hollow walls (with their convective air currents) are the mechanism that protects it.

    8) If you install insulation into these old walls without also installing a perfect air barrier that seals all wall penetrations, then you will be allowing moisture to still penetrate the wall (via wind- and stack-effect driven air movement) but will be removing the major mechanism for removing that moisture (convective air currents).

    This is a *huge* problem and is blamed for the outbreak of rotten/moldy houses in the pacific northwest.

    To summarize, to keep you from turning your 100 year old house into a rotten/moldy mess, you should either:

    1) Leave it as-is and swallow the monthly heating costs as an ongoing cost for keeping your house rot- and mold-free.

    2) Tear off all the siding. Install loose insulation in the walls by whatever method you prefer (e.g. blown cellulose). Add an air barrier (Typar/housewrap) to the outside of the house with particular attention to sealing *all* seams and *all* the wall penetrations to the air barrier. Reinstall siding. NOTE: Tar paper is *not* considered an effective air barrier by CMHC unless all seams are taped. In that case, it will cause moisture problems if there is poly on the inside surface of any of the walls. Picture a tuna sandwich left in a sealed ziploc bag...

    3) Blow *closed-cell* foam into your walls. No need to remove all the siding. No need to install a separate air barrier. Closed-cell foam *is* considered an air barrier if it's over 2" thick, so you can get the same results as #2 by *blowing* closed-cell foam into your walls. Foam board is *not* an equivalent because the gaps around the edges prevent it from acting as an air barrier.

    Does this help?
    Last edited: Jan 17, 2009
  15. jch

    jch Member

    One more thing...

    I forgot to mention that flashing all wall penetrations is also very important. The window sills on old houses serves as the flashing for the bottom of the windows, but you'll still need to install flashing at the top of every window/door if you decide to insulate.

    A 20 mph wind can blow water up (yes, up) about 4" behind shingles/clapboards. So CMHC recommends that flashing extend at least 4" up the wall (or, better yet, 6") to avoid wind-blown penetration of water into the wall.

    A "rain-screen" design is even better (and is required on all new construction here). Basically it's a 1/2"+ air gap between the siding and the air barrier. Typically, 1" strips of 1/2" pressure-treated plywood are installed vertically (along each stud) over top of the air barrier. The siding is then attached to these strips, with bug screens along the resulting gaps at the top and bottom edges of the wall.
    Last edited: Jan 17, 2009
  16. frenchie

    frenchie Jack of all trades

    Where in BC, John? I used to live in Vancouver.
  17. jch

    jch Member

    Victoria :) Very wet here.... (as you know)...

    I've got a stucco house with no insulation in the main floor walls. When we bought it back in 2002, the first thing I was going to do was blow cellulose into the walls.

    Then I took the CMHC course and saw what a disaster that would be.

    My plans now are to:
    - wait until the roof needs replacing
    - remove all the stucco
    - extend the eaves so the overhang is 24" (currently ranges from 1/2" on gable ends(!) to 8" on sides)
    - apply 2-4" of rigid foam insulation to the exterior (all seams taped with Red Tuck Tape), extending all the way down to the foundation's footings
    - install flashings (with end dams) over every window/door
    - wrap the house in Typar (as an air barrier), all seams taped with Red Tuck Tape
    - install vertical strips of 1/2" pressure-treated plywood, coincident with studs
    - parge the outside of the foam insulation from 6" above grade downward
    - install factory-painted Hardi-Board, end-painting and caulking all end-cuts
    - relax and forget about it.
  18. Master Brian

    Master Brian DIY Senior Member

    jcg, that does help.

    Sounds like I should just forget about it. I'm not going to remove all the siding and wrap the house. Even doing it myself, I probably wouldn't gain anything cost wise. Maybe rebuild the windows, which is a given, and install storm windows. As I rebuild the windows I'll probably insulate the cavities, with spray foam, where the sash weights go and install the spring type spring type of lift. That should cut down on air penetration around the windows. All-in-all, this house doesn't feel very drafty, except by a few windows which have issues with glazing....

    There isn't an issue with foaming the window cavities are there?
  19. frenchie

    frenchie Jack of all trades

    As long as you use the stuff for windows. The regular stuff expands so much it can bow the frames.
  20. Master Brian

    Master Brian DIY Senior Member

    Yes, it would be the window stuff.

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