The Challenge of Exterior Doors

My struggle to find reasonably energy-efficient exterior doors for our new house

The wood-like fiberglass door we found for our farmhouse. Click to enlarge.Photo Credit: Alex Wilson

Despite the chilly (seasonable) weather, work is progressing on the renovation/rebuild of our house in Dummerston. Last week, the three exterior doors were installed. Which brings me to one of my pet peeves: the lack of really good choices for highly energy-efficient exterior doors.

We ended up with a solution that I think will be okay, but there is a huge void in the world of truly high-performance doors. Here, I’ll describe the three doors we put in. I hope you can put up with my whining.

The front door

The purpose of front doors, I’m told, is to look nice. But I also wanted a front entrance door that would remain stable and airtight over many years or service and that would provide reasonable insulating value. Oh, and I didn’t want to spend more than about $2,000 for it. That proved a challenge.

I would have loved to install one of the gorgeous custom entrance doors made by Steve Benson’s company, J.S. Benson Woodworking, in Brattleboro. They are custom-fabricated of durable and highly stable triple-laminated mahogany (sustainably produced wood certified by the Forest Stewardship Council is available), but as solid wood, there is very little insulating value: maybe R-3 for a 2-3/4”-thick door.

For Benson doors with lites, the energy performance gets a little better, because Steve has access to super-high-performance glass from Alpen Windows in Colorado. Those lites can provide an insulating value of R-5 or even more—significantly higher than the solid door.

Steve’s beautiful doors have one other drawback: they cost an arm-and-a-leg, starting at about $5,000. A little rich for our budget.

Remarkably wood-like face of our Jeld-Wen door. Click to enlarge.Photo Credit: Alex Wilson

A high-end fiberglass entrance door

When I was researching doors for the house at Leader Home Center, I came across a Jeld-Wen door made of fiberglass but with a knotty-alder grain that looks remarkably like real wood—and I say that as someone who pays close attention to wood and can readily distinguish most species based on the grain. One could easily be fooled into thinking this door was real alder!

This door looked good. It was solidly built, yet it had a polyurethane insulation core, significantly boosting its R-value. I had already researched fiberglass vs. steel, and found that most energy experts preferred the former, even though magnetic weatherstripping can be used with steel.

“That’s the one I’d like,” I told Russ Chapman at Leader, referring to the knotty-alder floor sample. (Russ had been incredibly patient with me as I picked his brain for energy-performance information.) He said he’d price it out and get back to me.

Oops. It turned out that Jeld-Wenn had discontinued that model as a stock item; that particular door had been on display for three years. A similar door was still available, but it’s now a fully custom, hand-made option, and instead of costing around $2,000, it was going to cost something like $10,000!

“So what about buying this display model,” I asked Russ? It had a few dings, but would suffice. He figured out a nice price for it (the floor model wasn’t doing them much good, since that door wasn’t really available anymore as a reasonably affordable product).

Because we couldn’t get a matching side-lite in the same knotty-alder wood, we had the door hung with a totally different, painted side panel. The glass for that side panel is reasonably good: double-glazed with at least 5/8” separation between the panes of glass, argon-fill, and a low-e coating. We went with a continuous glass panel to minimize the greater edge losses that occur with true divided lites. I think it will look great when the house is sided.

A much less expensive fiberglass-core back door. Click to enlarge.Photo Credit: Alex Wilson

Cheaper back and side doors

For the back door into the porch and side door into the garage we wanted less expensive doors that were going to be well-insulated and tight. We opted for fairly run-of-the-mill fiberglass doors with upper glazing panels; these are also made by Jeld-Wen and cost us about $300 apiece.

These aren’t anything like the wood-like fiberglass entrance door in appearance (you could never mistake them for real wood), but like the front door, they have a polyurethane insulation core. Because there’s less structural reinforcing material in these doors, they may actually outperform the front door from an energy standpoint. I’ll be very curious about this and will plan to do some thermographic (infrared) analysis once the house is completed and lived in to study heat the relative loss through the different doors.

We still need better door options

I think the three exterior doors we ended up with provide a reasonably good compromise in appearance and performance. But compared with other energy features of the house (R-40 walls, R-50 roof, mostly triple-glazed windows, etc.), the doors are still a weak link.

I would love to see a high-quality, durable, energy-efficient, and reasonably affordable door introduced. Even at the high end—where customers have unlimited budgets and want to create a dream house that can be heated using solar panels on the roof—well-insulated doors are very hard to find. In Europe there are some good doors used for Passive House projects, but these tend to be very expensive.

Is anybody looking for a product development opportunity?

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.