Energy IQ / Comfort IQ / Build IQ
Exterior doors: compare the complete opening
Make sense of solid wood, insulated steel and fibreglass, patio-door styles and the ratings that describe the door you will actually receive.
Our articles are a starting point, not a professional assessment of your home.
DraftA work in progress, prepared by the HouseIQ.pro team.Editorial and professional review are not yet complete.
The slab is only part of a door
A door has several opportunities to lose heat or admit a draft: through its panel, through glass, around its moving edges and around the frame where it meets the wall. A thick panel can perform well while a worn bottom seal lets air pass. Treating those as different problems helps you avoid replacing a sound door when it needs service, or buying a better slab while retaining a troublesome opening.
The complete system includes the slab, frame, hinges, latch, weatherstripping and sill. Glass beside or above it adds sidelites or a transom to the entry. Ask the seller to identify exactly what is included in the quotation and rating. Therma-Tru’s component explanation is a useful illustration: even the astragal, the meeting detail between double doors, contributes to air and moisture control.
Look beyond the material on the surface
Solid wood and an insulated core covered by a wood, steel or fibreglass skin are different constructions. NRCan describes insulated-core doors as more thermally resistant than solid-material doors. That is a useful starting point, not a ranking of every finished entry system. Glass area, edges, panel thickness and the frame still affect the result. A description such as “solid core” needs clarification: what is the core, and what performance does the complete product have?
For a current example, Therma-Tru identifies polyurethane foam inside its Fiber-Classic fibreglass doors. The insulation benefit comes from that construction, not simply from the word fibreglass. Its published comparison with wood expressly concerns doors without glass. It would be misleading to transfer such a slab comparison to a heavily glazed entry, or to infer that all fibreglass products outperform every insulated steel door.
| Description | What to establish |
|---|---|
| Solid wood or “solid core” | Actual core construction, complete-product rating and exposure limitations |
| Insulated steel or fibreglass | Core, frame and edge design; exact glass option; finish and repair requirements |
| Glazed patio door | Whole-door U-factor, solar gain, air leakage and operating configuration |
Compare equivalent ratings, not headline R-values
R-value describes resistance to heat flow; a larger value means more resistance. A centre-panel claim does not describe every path through an opening. For shopping, a certified whole-product U-factor is more useful than an unqualified slab R-value: lower U means less heat transfer under the rating conditions. Ask which assembly and test or certification the number represents, rather than assuming two sales brochures have measured the same thing.
NFRC’s door label identifies ratings for the specific glass configuration. Changing the glass can therefore change the comparison even when the collection name remains the same. Keep the product code, size and glazing description with each quote. Canadian and U.S. documents can also use different units for U-factor; have the seller put competing figures in the same units. A rating comparison is evidence about the product, not a forecast of your household’s annual bill.
Glass changes the comfort conversation
A broad view through a patio door brings the glazing into the centre of the decision. U-factor addresses heat transfer; solar heat gain coefficient, or SHGC, describes admitted solar heat. A lower SHGC reduces solar gain. It is a separate characteristic, so “more insulating” does not automatically mean “blocks more sun.” Ask for both values for the exact glass package, including decorative glass or between-glass accessories.
For a Canadian room used through winter, insulation and interior comfort may carry considerable weight. Summer overheating still deserves attention. In Florida, sun exposure and cooling needs can make solar control particularly valuable, but a shaded opening and an unshaded west-facing opening are different situations. Andersen offers multiple glazing choices within its patio-door families; their existence is a reminder to compare configurations against the room’s needs rather than buy by style name.
Sliding versus French: separate movement from appearance
Sliding doors move along a track and avoid taking up a swinging arc in the room or on the patio. Hinged doors need that clearance; configurations with two operable leaves can provide a broad opening. “French” can describe the familiar glazed panel proportions as well as a hinged arrangement. Confirm which panels move, which remain fixed and how much clear passage is available before comparing performance.
A hinged arrangement can use compression seals, while sliding assemblies need seals that accommodate movement. Neither description establishes a universal energy winner. Compare actual U-factor, SHGC and available tested air-leakage information for the configurations under consideration. Also try a showroom example: a door that is difficult for the household to close and latch properly presents a practical problem that a favourable laboratory rating cannot solve.
A good seal is a matched, serviceable detail
Weatherstripping must make continuous contact while allowing the door to move and latch normally. Compression gaskets, magnetic seals and sliding profiles work differently. More material is not automatically better: an unsuitable profile can interfere with closure. On double doors, ask how the meeting edges and bottom corners are sealed; on a sliding door, ask about replacement seals and the condition of the track and operating hardware.
Think beyond the first day. Can the specified seals be replaced, and is the replacement profile identifiable? What maintenance does the manufacturer require? Therma-Tru describes its weatherstrip, glass and door components as a coordinated system. That is useful as a compatibility principle, not a reason to assume every generic replacement will reproduce the original performance. Our weatherstripping article explores the individual seal types in more detail.
The threshold has to manage feet and weather
The threshold is both a crossing point and a weather detail. A household may need easy passage for a walker, stroller or wheelchair; an exposed opening also needs suitable water resistance. Ask the supplier and designer to resolve those needs together. A low profile by itself is not evidence of either accessibility compliance or good performance in wind-driven rain.
The sill and surrounding flashing need a defined outward drainage route. The wall-to-frame air seal is another connection. These functions can coexist, but indiscriminately covering openings with sealant can defeat intended drainage. Ask the installer to explain the approved detail for this door and wall, including what remains visible for inspection. The separate flashing article follows that hidden water path without turning a generic drawing into an installation recipe.
Energy ratings do not replace exposure requirements
A sheltered front entrance and a coastal patio opening face different demands. Overhangs reduce direct wetting, but they do not replace a suitable product and wall connection. In Florida and other storm-exposed locations, have a qualified local professional establish the required wind, impact and water-resistance evidence for the exact opening. An energy label does not establish those properties.
Current Andersen information distinguishes its impact-resistant patio options from the ordinary configurations. This is a helpful example of why a collection name alone is incomplete. Ask which options and approvals are actually included in your order. Likewise, do not substitute an attractive exterior slab for a required garage-to-house separation door without professional confirmation of the complete assembly and its safety requirements.
Decide what needs repair before ordering replacement
A door that has become hard to latch may have worn hardware, damaged seals or an opening that has moved. Water staining or deteriorated material requires investigation before new trim hides it. Record when drafts or wetting occur and where they appear. An assessment can distinguish a serviceable door with a local defect from an assembly whose frame or concealed connection needs more extensive work.
For a replacement proposal, compare the same scope: product, glass, hardware, seals, sill, wall connection and finishing. Ask what happens if concealed damage is found and who documents the work before it is covered. Request care instructions and product identifiers at handover. Those records make future maintenance easier and preserve a useful explanation of what you chose, rather than leaving only a material name and a sales receipt.
Questions worth taking with you
- Does this rating cover the actual door, frame and glass configuration in the quote?
- Are the U-factor values expressed in the same units, and what air-leakage evidence is available?
- Which panels move, what clear opening remains, and can everyone close and latch it comfortably?
- How are the bottom corners, threshold and meeting edges sealed and maintained?
- What exposure approvals and concealed wall-connection work are included?
Sources
- Natural Resources Canada Keeping the Heat In — Section 8: Upgrading windows and exterior doors
- National Fenestration Rating Council What does the NFRC label tell you?
- Therma-Tru Fiber-Classic Collections
- Therma-Tru Product Education
- Therma-Tru Learn About Energy-Efficient Products
- Andersen Windows & Doors French Doors & Hinged Doors
- Andersen Windows & Doors Sliding Glass Patio Doors
- U.S. Department of Energy / Pacific Northwest National Laboratory Windows and Doors are Fully Flashed