Image Credit: Image #1: Martin Holladay
More Musings of an Energy Nerd
Almost every house has at least two exterior doors. A bad exterior door is ugly, leaky, made from materials that injure the planet, and has a low R-value. A good door is attractive, doesn’t leak air, is manufactured with materials that are harvested or produced in a sustainable way, and has a decent R-value.
Some architects design the main entry door to impress visitors who walk up to the house and ring the doorbell. But very few visitors arrive on foot, so most homeowners no longer need to impress doorbell-ringers. These days, most visitors park in the driveway and enter a house by the side door, just like family members.
Door materials
There are two basic categories of exterior doors: solid doors (usually made of wood) and insulated doors (usually make of polyurethane foam protected by skins of steel or fiberglass).
Solid wood doors are expensive. If you can afford a solid wood door made out of a durable species of wood, and you like the look, that’s probably the way to go. Note, however, that the R-value of a solid-wood door is lower than the R-value of an insulated steel door or fiberglass door.
If your exterior door is exposed to splashback, especially splashback mixed with rock salt (a problem in regions of the country where salt is spread to help melt ice), a steel door will eventually rust. That’s why fiberglass doors are preferable to steel doors.
Does R-value matter?
A solid wood door will have an R-value of R-2 or R-3. An insulated steel or fiberglass will have an R-value that is twice as good — generally R-5 to R-6, but in some cases as high as R-7. European manufacturers of Passivhaus-certified doors advertise R-values as high as R-11.
Energy Star doors without a glass…
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32 Comments
Multi-point locks?
Martin - have you seen any research on how much multi-point locks help? We've been ordering them as upgrades to fairly standard doors, and we think it makes a difference for air-sealing, but I'm not sure I'd bet the farm on it. They're fairly expensive, so it may not be a worthwhile expense.
Response to Dan Kolbert
Dan,
There is no doubt whatsoever that multi-point locks help hold a door against the weatherstripping and thereby reduce air leakage.
However, I have never seen anyone try to quantify the energy savings or calculate whether the projected energy savings are enough to justify the cost of the upgrade. Anyone care to try to make a stab at such a calculation?
No choice here
As part of the new energy requirements in our building code, which have also been adopted by other provinces, all windows and doors have three point locks.
It adds about $400 to the price of an exterior door. Not too bad when you are dealing with an expensive main entry, but an appreciable increase in the cost of (until now) cheap secondary doors.
Part of this comes from that it is a lot harder to install the hardware. Where I used to do it myself, the supplier now sends out their own installer.
Given that the last house I built had four exterior doors, and that the total annual heating costs are under $2000, that's a long ROI no matter how you slice it.
Air leakage and multi-point locks
I think multi-point locks do help air leakage, but I haven't been able to prove it. On most, you can close and latch the door without engaging the additional latches, or you can twist the handle to engage them. I had a blower door set up at my house recently, and I tried to see the difference in CFM50 with and without the additional latches engaged. I couldn't see any difference in the ~550 CFM50 I was measuring, and I couldn't detect noticeable leakage around the door with or without them engaged. On the other hand, there was noticeable leakage around the ordinary fiberglass pre-hung door with a single-point latch that we had recently installed for another entrance.
So what does that mean? Perhaps the installation was a little better on the multi-point locking door, and the difference has nothing to do with the latching mechanism. Or perhaps the other door has warped a tiny bit in the year since it was installed, and the multi-point door, being held flat when it's closed, is less prone to that problem.
But regardless of the results of my inconclusive experiment, I'm convinced that if I were to put a multi-point latch on the one that leaks, I'd improve it. And I'm also convinced that the door with the multi-point latch will continue to seal well longer than it would with an ordinary latch.
Is it worth the extra $400? Probably not for the energy savings, but perhaps for the satisfaction of closing the door and seeing and feeling it seal nicely.
And maybe I'll try that experiment again after I finish sealing a few other more minor leaks, such that I'll be measuring a smaller total and be able to detect a smaller difference in air leakage.
Charlie
They also offer enhanced resistance to break-ins, although I don't know to what extent that is much of a deterrent to a determined thief.
Response to Charlie Sullivan
Charlie,
Thanks very much for sharing the results of your experiments.
Until I read your comment, I hadn't thought about the implications of occupant behavior when it comes to multi-point locking mechanisms. You wrote, "You can close and latch the door without engaging the additional latches, or you can twist the handle to engage them."
I'm guessing that most homeowners are just going to slam the door as usual, and will rarely engage the multi-point locks. It's a little like buying triple-track storm windows, and leaving the windows up all winter...
storm door with magnetic seal may have a role with antique doors
I've found that a storm door with a magnetic seal has improved the airtightness of our antique wooden entry doors which are hard to weatherstrip completely tightly, particularly at the threshold. Larson still makes one such model (they used to have additional, more attractive models available with this feature). I would think too that airtight storm door would add R-value to an existing door with a single-pane lite, like a storm window does.
Single-point success, mostly
On single-point vs multi-point, I've had very decent success with both from an air-sealing point of view. The constraint has been long-term dependability, particularly with the single (no surprise there.)
On my first Passive House, as the one paying all the bills with a stretched budget, an extra $2000 for the 4 entry doors was not available. We started with a standard $200 package: wood jamb, single gaskets (simple Q-lon, kerf-insert, compression style), Therma-tru fiberglass R-8 panels and a Schlage handle/deadbolt combo. Then augmented with a custom threshold and ensured good seals (short piece of 1/4" backer rod behind gaskets at top corners and those seemingly silly wedges at bottom), we reached the goal pretty much perfectly with no perceptible infiltration at 50P. There was notably more air-leakage at the fiberglass windows but still reached ~200cfm @50P/ 0.43ACH50.
The single Q-lon gaskets are generally notorious for sustaining damage due to use/abuse and simple door strikes require vigilance so this is not great from a long-term w/ low-maintenance viewpoint. They are all simple materials and very available but it seems I do need to adjust at least one element a year.
For a Passive House occupied this past Spring, one utility room door used this technique where the remaining ones were multi-point. All were equally air-sealed however the utility room will only see rare use/abuse so it's simpler seal should last.
With that in mind, for higher-exposure locations, almost all wood doors and more heavily-used doors I definitely recommend a multi-point lock to clients. One simple maintenance call could easily consume much of the additional upgrade and they have much greater capacity to address long-term building movement/ door distortion.
Response to Harry Voorhees
Harry,
You're right, of course, that a storm door can reduce the air leakage rate through an entry door, and can add R-value to the door assembly. No one is disputing those facts.
The question is whether the energy savings attributable to a storm door are enough to justify the cost of installing the door -- in other words, whether the measure is cost-effective. To my knowledge, all researchers who have looked into this question have reached the same conclusion: the measure is not cost-effective.
R value
I would argue that a door's R value does matter when trying to build a super insulated home. Let's consider an example of a 3'x7' door with R3. If the walls are R40, you are losing the same amount of heat as a 28'x10' foot section of wall! Add 3 or 4 exterior doors, and the heat lost through the doors can be more than 50% of that lost through the walls.
Response to Daniel Beideck
Daniel,
Let's compare an R-6 door that costs about $300 with an R-11 Passivhaus door that costs $4,000.
The R-11 door will save about $4.70 per year in energy costs. That means that the payback period for the $3,700 upcharge is about 787 years. I don't think that the Passivhaus door will last that long, so the upgrade will never pay for itself.
Here's the math (assuming an average delta-T of 40 F° for a 6-month heating season):
Heat loss rate in BTU/h for an R-6 door: (21 * 0.166 * 40) = 139 BTU/h
Heat loss rate in BTU/h for an R-11 door: (21 * 0.09 * 40) = 76 BTU/h
The difference is 63 BTU/h, which = 18 watts = 0.018 kW
Per month: (0.018 kW * 24 * 30) = 13 kWh of heat energy
For a season: (13 kWh *6 months) = 78 kWh of heat energy per season
Providing this heat energy with a heat pump with a COP of 3 requires 26 kWh of electricity per year
Assuming that electricity costs $0.18 per kWh, annual savings is $4.70
Why buy a nice door
If you go to a door and window show room, you will find a vast range of doors from perhaps $300 to $6000. In most such showrooms in the US there will be very little difference in energy performance. The high-end doors are purchased for aesthetics and as status symbols. The way a door works as a status symbol is complicated--it has to show that you have enough money to buy a fancy door, but that you have good enough taste to buy something understated. This works out very well for door companies, because they can offer each tier at a 2X higher price, even though it only costs a little more to make. That way they get to extract the maximum affordable price from every customer, and a little more than the maximum affordable price from customers who aspire to a higher income bracket than they are currently in.
But marketing high-end doors is tricky. Since high-end customers are trying to show that they have more refined taste than purchasers of mass-market doors, the high-end market splinters into different segments with different subtle criteria that only expert consumers know about. Is the wood door assembled with true mortise and tenon joints? Was it hand planed? What species of exotic tropical hardwood is it made from? And, for one of the narrowest segments--GBA readers--is it passive house certified, and can it help you set a record for how far below 0.6 ACH50 you can get?
You can argue that such expenditures are a waste of money. But if you consider spending on status symbols to be a given, it's a good thing to direct such spending to something that saves even a little energy, vs. spending it on, for example, unsustainable harvesting of tropical hardwood.
It's still worth doing the math--perhaps scaling back from a passive house to a pretty-good house allows saving enough money to put a Tesla in the driveway. In some scenarios that would provide a greater reduction in carbon emissions, and in some circles, that would go further as a status symbol, particularly given that you can be seen in it driving around town.
And it's worth putting solid information on cost effectiveness out there, just in case some readers are interested in saving money.
Response to Martin
The current costs for a higher performing doors that Martin points out are the reason the super-insulated house I built has standard low R doors. Nonetheless, my point is still valid, i.e. a substantial amount of the heat lost in a super-insulated home with standard doors is through those doors. I believe it's important to first acknowledge the problem so that it might be solved.
I highly suspect the reason an R11 door is so much more expensive than an R6 door is the lack of demand and not from higher material costs or the like. And as long as the price stays that ridiculously high, the demand will stay low. However, that doesn't mean the need doesn't exist or that the price wouldn't drop dramatically should we get to the point when the higher performing doors are manufactured in greater quantities etc. Hopefully, the day will come soon where buying a thicker, better performing door makes economic sense in addition to environmental sense.
Response to Daniel Beideck
Daniel,
Whether the heat loss through a door is "substantial" depends on your point of view. You have chosen to compare the door to an area of windowless wall rated at R-40 -- a type of wall assembly with an extremely low rate of heat loss. So what?
My point still remains: switching to an R-11 door is only going to save $4.70 per year.
If a homeowner wants a 20-year payback to the upgrade to an R-11 door, then manufacturers have to find a way to build an R-11 door for only $94 more than an R-6 door. If they can do that, then homeowners who care about payback might sit up and pay attention.
weak link
I estimate that something like 10% of the heating necessary for my super-insulated, passive solar home is due to the conventional exterior doors I used. On a per square foot basis, that is the weak link in the shell with the possible exception of the North facing windows. For those reasons, I consider the heat loss through the door to be substantial and significant.
Unlike the windows, however, future improvement seems relatively straightforward if we are willing to acknowledge the issue and look beyond the current cost differential. Getting to R11 from a R6 door shouldn’t be much more difficult than building a fiberglass shell around a 2” piece of insulation rather than something nearer to 1”. If done in large quantities, I’m not sure the cost difference needs to exceed $100. At that price, people only concerned about the net cost should come aboard too. Meanwhile, those of us that care about more than money should at least acknowledge the weak leak if we hope to improve upon it, in my opinion.
US Made higer R-value entry door
I did find this US made door that seems to have higher R-values & better glazed glass but it does not look like it is available with multi-point locking:
https://www.provia.com/productdetail/entry-doors/embarq-door
Does anyone have any experience with this door?
Response to David Stein
David,
Thanks for your comment. I'm not familiar with Provia doors. Are there any GBA readers who can share their experience or knowledge on this topic?
Here is the contact information for the company:
Provia Doors
2150 State Route 39
Sugarcreek, OH 44681
800-669-4711
330-852-4711
Fax: 877-735-2057
http://www.provia.com
Upgrade door and sill?
It's been tough to find a traditional looking door to match a historic house that has decent performance (short of going fully custom for ~$10,000)
One thought is to buy a stock Simpson door and spend a grand upgrading the threshold and gasketing. Sure, it's an R2 door, maybe R3 given thickness but my hunch is that air infiltration is the biggest source of loss.
Thoughts?
Response to Edward Cambridge
Edward,
I'm not familiar with the quality of Simpson doors, so I can't comment on your choice of that brand.
Q. "Sure, it's an R-2 door, maybe R-3 given thickness, but my hunch is that air infiltration is the biggest source of loss. Thoughts?"
A. Here's my thought: It sounds like you read my article. I wrote, "You probably don’t want to obsess about the R-value of your entry door. Heat loss through two or three exterior doors represents a very small portion of your home’s energy use, so big increases in door R-value don’t translate into big savings on your energy bill. ... In most cases, air leakage around the perimeter of an entry door is a greater concern than a door’s R-value."
No ROI
This article clearly places emphasis on the incredibly long ROI time for high-end energy efficient doors (longer in many cases than the life of the door according to the above).
Yet I see in many older Q&A's and blogs talk of searching for Passivhaus standard doors with little to no mention of the poor ROI in these discussions (here on GBA). Is this realization simply somewhat newer than these discussions, or is it simply that these other discussions have moved beyond the ROI, choosing to focus on reaching 'the goal'? I ask not to call anyone out, only to wonder why this appears to be the only article (that I readily found, I'm sure Martin will link me to a dozen others) that highlights the incredibly poor ROI of expensive high R doors.
Despite the math provided by Martin, intuitively, its hard for me to grasp why the R value of a door essentially matter not at all, while windows seems to be such a big to do. Is the math really that different on windows?
note: I have read "Study Shows That Expensive Windows Yield Meager Energy Returns" yet it seemed to say that the 'really high end' didn't have a payback, but still recommended 'affordable' triple glazed. The tone of this "all about doors" piece would lend me to think that having crappy R value for a relatively small square in the envelop doesn't matter at all, so long as its tight. Is it simply that the cumulative hole is larger with windows?
Response to Tyler Keniston
Tyler,
In Comment #11 on this page, I provide a back-of-the-envelope analysis showing the absurdity of thinking that there will be a return on investment (from an energy savings perspective) for the purchase of a $4,000 door.
Although I have consistently pointed out, in article after article, that the large investments required to reach the Passivhaus standard make little economic sense, I nevertheless provide answers to Passivhaus builders who post questions on our Q&A page -- questions such as, "Where can I buy a Passivhaus-certified entry door?" I answer those questions because it is one of the services provided by GBA. But just because I answer the question, doesn't mean I think it makes sense to pay $4,000 for an entry door.
If I berated every builder who posts a question, accusing the builder of stupidity, readers would be turned off. That said, thoughtful readers of GBA will come to know my philosophy -- one that aligns more with the Pretty Good House movement than the Passivhaus movement.
Here are links to articles that address some of the questions you raise:
Are Passivhaus Requirements Logical or Arbitrary?
Deep Energy Retrofits Are Often Misguided
developing personal philosphy
Thanks Martin, that all makes sense.
I am new to the 'green building' world and am working to develop my own philosophies (which are of course not static entities). I asked the above question to help improve the clarity of others' thoughts as I perceive them and to earnestly inquire if anything has shifted in the discussion on high end doors (and their ROI). There seem to be a lot of moving targets in this world.
I appreciate your response, and everything the GBA community provides. Along with tremendous amounts of technical information, I find the philosophies/nuanced perspectives of those with many years of experience invaluable. As a seeker of perfection and as an all-in kinda person, it is the wisdom of restraint, balance, and big picture thinking that can be most helpful to me when it comes to making hard decisions and working within a budget.
Sometimes it almost feels like if true efficiency in every aspect of society is what we seek, we need an algorithm to determine the best move of... well every individual. Not to say this is a reality I want to live in, but perhaps would yield the most true systems efficiency. But I digress from doors...
Boiling a frog
Regarding ROI on doors and the importance of R value on doors.. what I have found in designing and building is that at each turn, each little item will seem to have a negligible effect on overall building performance - but the cumulative effect of good decisions can perhaps be profound. Moreover, what I have found is that it is the increased performance of low-R value items which greatly improves overall building performance. It doesn't sound exciting to move from R-1 to R-2, or from R-3 to R-4, but it in these transitions that real building performance enhancements can happen. (and in reduction of thermal bridging on larger components.
Regarding sliding vs hinged- "Once you realize that air leakage matters more than R-value, you’ll intuitively understand why hinged doors are preferable to sliding doors. Sliding doors leak a lot of air. If you want a pair of doors with big panes of glass, make them French doors, not sliders.
Some sliding doors have better weatherstripping systems than others. If you have your heart set on sliding doors, you can look at so-called “lift-and-slide” doors — a category of doors that aren’t as leaky as old-fashioned sliders."
A lot of times sliders save space on either side of the door, and it's sometimes not practical to have a hinged entry/exit to a porch or deck. Sounds like the best option in this case is "lift-and-slide"?
How much of an improvement in air leakage is that? (assume it still doesn't compare to french door). Is it a lot more expensive?
Does the lift/slide technology exist for sliding windows too?
User-7379861,
First of all, can you tell us your name? (I'm Martin.)
I don't have a way to quantify the difference in air leakage between ordinary sliding doors and lift-and-slide doors -- and in any case, the actual air leakage numbers will vary by manufacturer and circumstances (wind speed, etc.). I was speaking in generalities, and I stand by my advice.
Is the upcharge worth it? The answer to that question depends on your budget, and how you value comfort.
To find out what the upcharge is, you would obviously have to contact door distributors and ask for some prices.
When it comes to sliding windows, the better option you are seeking is called "tilt/turn." Tilt/turn windows are standard in Europe, but they are increasingly available in the U.S. (Other options include casement windows and awning windows.)
This isn't meant as a plug for the product or Risinger but in this video they talk a lot about sliders and DP or PG ratings. While those are intended for water and wind performance, might they have some correlation to air leakage? At least in the case of the Marvin multi-slide they're discussing, it seems like the air sealing gasket on the bottom meant to improve DP might also reduce infiltration. So would a higher DP/PG door have lower infiltration?
https://www.youtube.com/watch?v=8XLe2vBLPZs
Are multi-slides usually considered poor-performing (like regular sliders) compared to lift and slides?
I'm somewhat surprised that there are no comments on inswing vs outswing, especially in the air leakage discussions. For example, I have a deck exposed to wind so I'm thinking outswing French doors there would be the better choice. In general, is it now a consensus that you're better off with outswing if you can get away with them or does the pressurization of a relatively well sealed and ventilated home offset the benefits?
Ron Weldy
Ron,
Social conventions on whether doors should swing in or out are well-established and unlikely to change. Residential doors swing in, because this approach is more welcoming to guests and less likely to cause problems on small stoops or entry porches. Exterior doors on commercial buildings swing out for fire safety reasons. Everyone is familiar with these conventions, so those who want to do things differently will confound visitors and door users.
In addition to the reasons Martin notes, exterior doors often have a screened door. On the one occasion I had a client who wanted an outswing entry door, they decided to put a screened door on the interior, which looked odd and was covered with light-seeking bugs on summer nights. If they opened the screened door the bugs would enter the house. (On screened porches I use outswing doors for the same bug-control reason.)
Good points. I definitely would not consider outswing for the main entry door, as it would be somewhat confounding to guests. But for the French doors on the deck, I will take the screening issues in consideration. I didn't really think of that, I see you can get them. BTW, site has been most helpful in planning our "to the studs" remodel. Loads of thanks!
"If you care about energy efficiency, it’s important to inspect the weatherstripping on your door once a year. If it shows signs of wearing out, you can buy new weatherstripping kits at a hardware store or home center."
In an otherwise excellent article this is one bit of terrible advice. Have you seen the crap they sell as weather stripping at home centers? It attaches with adhesive or nails, it's not going to stay put for long, it looks awful, and even when new it doesn't provide a good seal. Quality weather stripping installs in a kerf cut into the door jamb. Your best bet is to get a replacement seal from the manufacturer. Failing that there are aftermarket kerf style seals available. You can use drill bits as a gauge to measure the size of the kerf to get the right size.
DCC,
You sound conscientious, and your advice on weatherstripping will work for homeowners who are similarly conscientious. For those who want to reduce air leakage more quickly than would be the case if they tracked down the door manufacturer and ordered factory weatherstripping that is designed to be installed in the existing kerf, weatherstripping sold at a home center will reduce air leakage, if carefully installed. There is always more than one way to skin a cat.
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