All About Doors

musingsheader image

All About Doors

When green builders choose an exterior door, what features do they look for?

Posted on Nov 11 2016 by Martin Holladay
prime

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-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. . 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 PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates.-certified doors advertise R-values as high as R-11.

Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. doors without a glass lite must have a minimum R-value of R-5.8. Energy Star doors with a glass light that is no more than 50% of the door must have a minimum R-value of R-4 (see Image #2, below).

That said, 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.

Air leakage

In most cases, air leakage around the perimeter of an entry door is a greater concern than a door’s R-value. By all accounts, exterior doors from Europe (that is, doors costing between $2,000 and $4,000) have better quality weatherstripping than doors manufactured in North America. European doors available in the U.S. include doors by Intus and Drewexim.

Exterior doors with an Energy Star rating must meet a maximum air leakage rating of 0.5 cfm/square foot. (Although most Energy Star documents don't explain this rating, I assume that the required testing must comply with ASTMAmerican Society for Testing and Materials. Not-for-profit international standards organization that provides a forum for the development and publication of voluntary technical standards for materials, products, systems, and services. Originally the American Society for Testing and Materials. E283, and is performed at a test pressure of 1.57 PSF.)

Weatherstripping wears out. The older the weatherstripping, the higher the air leakage rate. 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.

Some entry doors have adjustable thresholds. If your door has an adjustable threshold (look for screws in the threshold directly under the door), it’s worth playing around with the adjustments. A minor adjustment can significantly reduce the air leakage rate.

Sliding or 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.

This large tilt-and-turn window is used as a door. The window/door was manufactured in Germany by Optiwin. The door is being demonstrated by homeowner Margaret Stanton of Urbana, Illinois. [Photo credit: Martin Holladay]

If you are concerned about air leakage, another option is to use a very large European-style tilt-and-turn window as a door (see the photo at right). European brands of tilt-and-turn windows usually have excellent weatherstripping.

Don’t forget roof protection

Every exterior door needs to be protected by a roof. This can be accomplished with a porch or a dedicated roof directly over the door.

If your door lacks roof protection, it’s only a matter of time before the jambs begin to rot.

Installation details

In most respects, exterior doors need the same type of flashing required for a window. The most important flashing element is a sill pan. For information on the flashing requirements for exterior doors, see these resources:

If you plan to install an “outie” door in a thick wall (either a double-stud wallConstruction system in which two layers of studs are used to provide a thicker-than-normal wall system so that a lot of insulation can be installed; the two walls are often separated by several inches to reduce thermal bridging through the studs and to provide additional space for insulation. or a wall with thick exterior rigid foam), you may need to use the “frame within a frame” method to ensure that the door can open fully. For more information on this issue, see:

  • A Fine Homebuilding article called Windows and Doors in Double-Stud Walls.
  • A Q&A thread on GBA called Detail for innie inswing door with thick exterior foam?
  • A Q&A thread on GBA called Exterior door details with 4-inch-thick foam walls.
    • If you intend to install an outie door at a house with thick exterior rigid foam, you may be asking the question, “How do I support the door threshold when the door ends up cantilevered beyond the foundation?” For more information on this issue, see a Q&A thread on GBA called Outie doors.

    What about storm doors?

    Storm doors will never save enough energy to justify their purchase price. A storm door is not cost-effective.

    In some cases, glass storm doors can damage your main entry door. If the door gets several hours a day of direct sunlight, the air between the storm door and the main door can get hot enough to damage door components.

    For more information on this issue, see A Storm Door is Not a Wise Home Energy Efficiency Improvement.

    Airlock entries and mudrooms

    An astronaut who wants to exit an orbiting spacecraft has to pass through two doors that create an airlock entry. But houses on earth don’t need an airlock entry.

    In the early 1970s, some energy-efficiency advocates promoted the idea that every house needs an airlock entry — basically, a mudroom. The idea was that a visitor would enter the mudroom and close the exterior door. Then the visitor would open the door from the mudroom to the house. That way, exterior air and interior air would never encounter each other directly. Presumably, this type of “airlock entry” would save energy.

    The idea made intuitive sense — until someone did the math. It turns out the opening an exterior door doesn’t increase your energy bills very much. Even if an airlock entry reduces infiltration slightly, the savings are too small to justify the expense of a mudroom.

    The bottom line: Build a mudroom if you want, but don’t tout it as an energy feature. It will never save enough money to justify the cost of building it.

    Martin Holladay’s previous blog: “Drainwater Heat Recovery Can Lower Your HERS Score.”

    Click here to follow Martin Holladay on Twitter.


Tags: , , , , , ,

Image Credits:

  1. Image #1: Martin Holladay
  2. Image #2: Energy Star

1.
Nov 11, 2016 9:02 AM ET

Multi-point locks?
by Dan Kolbert

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.


2.
Nov 11, 2016 10:35 AM ET

Response to Dan Kolbert
by Martin Holladay

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?


3.
Nov 11, 2016 12:04 PM ET

No choice here
by Malcolm Taylor

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.


4.
Nov 11, 2016 1:06 PM ET

Edited Nov 11, 2016 1:09 PM ET.

Air leakage and multi-point locks
by Charlie Sullivan

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.


5.
Nov 11, 2016 2:35 PM ET

Charlie
by Malcolm Taylor

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.


6.
Nov 12, 2016 5:39 AM ET

Response to Charlie Sullivan
by Martin Holladay

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...


7.
Nov 13, 2016 8:43 PM ET

storm door with magnetic seal may have a role with antique doors
by Harry Voorhees

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.


8.
Nov 14, 2016 3:47 AM ET

Single-point success, mostly
by Dan Whitmore

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.


9.
Nov 14, 2016 4:59 AM ET

Response to Harry Voorhees
by Martin Holladay

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.


10.
Nov 17, 2016 6:16 PM ET

R value
by Daniel Beideck

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.


11.
Nov 18, 2016 6:05 AM ET

Response to Daniel Beideck
by Martin Holladay

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


12.
Nov 18, 2016 8:56 AM ET

Why buy a nice door
by Charlie Sullivan

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.


13.
Nov 21, 2016 10:29 AM ET

Response to Martin
by Daniel Beideck

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.


14.
Nov 21, 2016 11:05 AM ET

Response to Daniel Beideck
by Martin Holladay

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.


15.
Nov 22, 2016 12:22 PM ET

weak link
by Daniel Beideck

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.


16.
Nov 23, 2016 2:03 PM ET

US Made higer R-value entry door
by Dave Stein

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?


17.
Nov 23, 2016 2:16 PM ET

Response to David Stein
by Martin Holladay

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
www.provia.com


18.
Jan 12, 2017 10:01 PM ET

Upgrade door and sill?
by Edward Cambridge

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?


19.
Jan 13, 2017 7:19 AM ET

Response to Edward Cambridge
by Martin Holladay

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."


Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!