{"id":406,"date":"2026-09-08T22:40:23","date_gmt":"2026-09-08T15:40:23","guid":{"rendered":"https:\/\/www.skala8.com\/blog\/windows-and-doors-terms-explained\/"},"modified":"2026-10-25T00:58:43","modified_gmt":"2026-10-24T17:58:43","slug":"windows-and-doors-terms-explained","status":"publish","type":"post","link":"https:\/\/www.skala8.com\/blog\/windows-and-doors-terms-explained\/","title":{"rendered":"Windows and Doors Terms Explained"},"content":{"rendered":"

<\/p>\n

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Two quotes arrive on your kitchen table, both for the same job, both plausible. One says full-frame replacement<\/strong>, the other says pocket replacement<\/strong>. One lists a U-factor of 0.24, the other calls the same window energy efficient. You cannot tell which deal is better without knowing the words.<\/p>\n

That vocabulary was written for the supply chain, not for the person paying the invoice. WDMA, the Window and Door Manufacturers Association, defines fenestration<\/strong> as openings in the building envelope, such as windows, doors, curtain walls, and skylights.<\/p>\n

Opening Terms: Which Rough Opening Measurement You Actually Order Against<\/h2>\n
\n\"A
Matching window operation terms to the right sash<\/figcaption><\/figure>\n

The rough opening<\/strong> causes the most confusion, because it means different sizes in different trades. WDMA defines it as the opening in a wall or roof into which a window or door is installed. Knockety calls it an unfinished opening where a unit goes.<\/p>\n

Knockety also defines a recess as a space in a wall into which another part can be fitted. That is why a window and a door in one wall get rough openings measured differently.<\/p>\n

Three frame names you will hear constantly: WDMA defines the head<\/strong> as the horizontal top member, the jambs<\/strong> as the vertical sides, and the sill<\/strong> as the bottom member. The interior door measuring guide<\/a> shows how those three set measurement.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Opening and frame terms every homeowner ends up measuring<\/caption>\n
Term<\/th>\nDefinition<\/th>\nWhy it matters<\/th>\n<\/tr>\n<\/thead>\n
Rough opening<\/td>\nUnfinished hole in the wall<\/td>\nOrder against this, not the window<\/td>\n<\/tr>\n
Recess<\/td>\nSpace in a wall<\/td>\nSets how deep it sits<\/td>\n<\/tr>\n
Jamb<\/td>\nVertical sides of the frame<\/td>\nWhere you nail, hinges live<\/td>\n<\/tr>\n
Head<\/td>\nHorizontal top member<\/td>\nCarries sash weight, flashing<\/td>\n<\/tr>\n
Sill<\/td>\nHorizontal bottom member<\/td>\nRots first, drains it<\/td>\n<\/tr>\n
Brickmold<\/td>\nExterior trim as casing<\/td>\nThe outdoor trim, an upgrade<\/td>\n<\/tr>\n
Finished opening and cut-out<\/td>\nThe opening after trim, and the hole actually cut<\/td>\nThe size you order against<\/td>\n<\/tr>\n
Apron<\/td>\nTrim board under a stool<\/td>\nCovers the gap under trim<\/td>\n<\/tr>\n
Miter<\/td>\nThe angled joint between trim<\/td>\nWrong angle, corner gap<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Window Terms: Double-Hung vs Casement and the Glass Inside<\/h2>\n

WDMA defines a hung window<\/strong> as one with vertically sliding sashes using counterbalancing devices, and a double-hung window<\/strong> as a hung window with two operable sashes. That is the whole difference from single-hung: how many sashes move, not price tier.<\/p>\n

A casement window<\/strong> is one with sashes hinged to open from the side, next to the jambs. WDMA groups awning and hopper as a window with sashes hinged top or bottom, awning out and hopper in.<\/p>\n

The glass side has its own vocabulary. WDMA defines airspace<\/strong> as the space between adjacent layers, and the spacer<\/strong> as the material holding it apart. The gap insulates, not the glass.<\/p>\n

WDMA also defines a divider as a member dividing glazing into separate vision areas, and notes that muntin means the same thing.<\/p>\n

The window glass replacement guide<\/a> shows what an airspace and a spacer look like when one fails.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Window operation and glazing terms, and where the money goes<\/caption>\n
Term<\/th>\nDefinition<\/th>\nWhy it matters<\/th>\n<\/tr>\n<\/thead>\n
Double-hung<\/td>\nTwo sliding sashes, both move<\/td>\nTwo-way ventilation, standard<\/td>\n<\/tr>\n
Single-hung<\/td>\nHung window, one operable sash<\/td>\nCheaper, one less leak path<\/td>\n<\/tr>\n
Casement<\/td>\nSashes hinged at the side<\/td>\nTight seal, sheds driving rain<\/td>\n<\/tr>\n
Awning and hopper<\/td>\nSashes hinged top or bottom<\/td>\nAwning out, hopper in<\/td>\n<\/tr>\n
Sash<\/td>\nMembers that hold the glass<\/td>\nThe moving part, leaks start<\/td>\n<\/tr>\n
Balance<\/td>\nDevice counterbalancing the sash<\/td>\nA bad balance causes sticking<\/td>\n<\/tr>\n
Insulating glass unit, spacer, airspace<\/td>\nLites sealed around a gas space held by a strip<\/td>\nThe gap insulates, not the glass, and a failed seal fogs<\/td>\n<\/tr>\n
Divider, muntin, glazing bead<\/td>\nA member dividing glazing, and trim holding the glass<\/td>\nStructural or decorative<\/td>\n<\/tr>\n
Laminated glass and tempered glass<\/td>\nLites bonded with polymer, or safety glass that shatters small<\/td>\nStays together when broken<\/td>\n<\/tr>\n
Fenestration cladding<\/td>\nExterior parts covering frame<\/td>\nProtects the frame, visible finish<\/td>\n<\/tr>\n
Weep hole<\/td>\nAn opening that drains water<\/td>\nBlocked, water sits and rots<\/td>\n<\/tr>\n
Slider and fixed window<\/td>\nSashes sliding horizontally, or a window that never opens<\/td>\nWide opening, one handle<\/td>\n<\/tr>\n
Sill pan and head flashing<\/td>\nA flashed pan at the base, and flashing over the window<\/td>\nCatches what the sill misses<\/td>\n<\/tr>\n
Screen<\/td>\nWire mesh, keeps out insects<\/td>\nNot a security product<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Performance Terms: Why U-Factor and SHGC Point Opposite Ways<\/h2>\n

The Two Numbers That Point Opposite Ways<\/h3>\n

Energy terms look like alphabet soup until you learn each measures a different thing. Heat through the glass is one problem, sunlight carrying heat another, and light getting through a third. Confusing them is how a good window ends up wrong for your climate. The window energy ratings guide<\/a> splits them apart.<\/p>\n

WDMA defines air leakage<\/strong> as the flow of air passing through the product, and design pressure<\/strong> as the rating for the wind or snow load it must withstand.<\/p>\n

WDMA defines certification<\/strong> as a process where a product line sample has been tested, meets requirements, and is under ongoing outside inspection. The window energy ratings guide<\/a> goes deeper on what those ratings mean for you.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n
Performance and certification terms and the practical difference<\/caption>\n
Term<\/th>\nDefinition<\/th>\nWhy it matters<\/th>\n<\/tr>\n<\/thead>\n
U-factor<\/td>\nRate of heat loss through it<\/td>\nLower is better, heating number<\/td>\n<\/tr>\n
Solar Heat Gain Coefficient<\/td>\nSolar heat through the glazing<\/td>\nLower for cooling, higher in winter<\/td>\n<\/tr>\n
Visible Transmittance<\/td>\nFraction of visible light<\/td>\nHigher for daylight, rated apart<\/td>\n<\/tr>\n
Air leakage<\/td>\nFlow of air through it<\/td>\nSometimes worse than the glass<\/td>\n<\/tr>\n
Certification<\/td>\nA tested line, inspected outside<\/td>\nOutside testing gives it value<\/td>\n<\/tr>\n
Low-E coating<\/td>\nA microscopic glass layer<\/td>\nLets light in, blocks infrared<\/td>\n<\/tr>\n
Argon fill<\/td>\nInert argon gas between panes<\/td>\nConducts less heat than air<\/td>\n<\/tr>\n
Operating force<\/td>\nForce to start or hold motion<\/td>\nA stiff sash is hardware<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Door Terms: Swing Direction, Hardware, and the Parts That Seal<\/h2>\n

Door hardware carries the vocabulary people mix up most. A hinge<\/strong> is the pivot point, handing<\/strong> is which way the door swings, the strike<\/strong> the jamb plate the latch enters, the latch<\/strong> the bolt.<\/p>\n

Knockety defines a transom as a decorative window above a door, weather-stripping as sealing openings from the elements, and the threshold as the part of the unit attached to the floor.<\/p>\n

The interior door installation guide<\/a> shows those parts on a real door instead of naming them in the abstract.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Door terms from hardware to weather seal<\/caption>\n
Term<\/th>\nDefinition<\/th>\nWhy it matters<\/th>\n<\/tr>\n<\/thead>\n
Prehung unit<\/td>\nSlab hung in its jambs<\/td>\nFaster install, frame squared<\/td>\n<\/tr>\n
Slab<\/td>\nThe panel alone<\/td>\nOnly if the frame is sound<\/td>\n<\/tr>\n
Hinge, pivot, latch and strike<\/td>\nThe pivot the leaf turns on, the axis it rotates about, the bolt, and the plate<\/td>\nLoose hinges swing uneven<\/td>\n<\/tr>\n
Mortise<\/td>\nA recess cut for hardware<\/td>\nWrong depth fails the fit<\/td>\n<\/tr>\n
Bevel, handing, swing direction<\/td>\nThe angled edge on a slab, which way it swings, and inward or outward<\/td>\nBevel must match the frame<\/td>\n<\/tr>\n
Casing<\/td>\nTrim covering the jamb gap<\/td>\nA different profile than window<\/td>\n<\/tr>\n
Transom<\/td>\nA window above a door<\/td>\nOften decorative, not egress<\/td>\n<\/tr>\n
Weatherstripping<\/td>\nSealing openings from elements<\/td>\nCheapest draft fix, often enough<\/td>\n<\/tr>\n
Threshold or sill<\/td>\nThe part on the floor<\/td>\nWhere water collects, decides rot<\/td>\n<\/tr>\n
Reveal<\/td>\nHow far the frame sits back from the wall<\/td>\nSets how deep the door sits<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Replacement Terms: What Each Method Costs You<\/h2>\n

Now the vocabulary that decides how much of your house gets torn up. A full-frame replacement removes the entire unit, frame and sill included. A pocket replacement installs a new sash into the old frame.<\/p>\n

Full-frame replacement gives the installer access to the rough opening, so the sill can be flashed and drained, the frame checked for rot, and gaps insulated. Pocket cannot reach that, and is right when the frame is sound.<\/p>\n

Quotes are written per unit<\/strong> and per opening, which differ, so the unit count tells you how many pieces you pay for. The interior door measuring guide<\/a> shows how slab size, unit size, and rough opening stack up.<\/p>\n

The rest is what gets added to the number. Flashing diverts water away from the opening, and labor separates a product quote from an installed one.<\/p>\n

A standard residential opening runs roughly $150 to $1,200 for the unit, with labor running $100 to $300 per window and $150 to $400 per door. The window and door installation cost guide<\/a> breaks those line items out<\/p>\n\n\n\n\n\n\n\n\n\n\n
Replacement method and cost vocabulary<\/caption>\n
Term<\/th>\nDefinition<\/th>\nWhy it matters<\/th>\n<\/tr>\n<\/thead>\n
Full-frame replacement<\/td>\nWhole unit removed with frame<\/td>\nLets the installer flash and inspect<\/td>\n<\/tr>\n
Pocket replacement<\/td>\nNew sash into the old frame<\/td>\nFaster, cheaper, leaves rot<\/td>\n<\/tr>\n
Per unit and per opening<\/td>\nPricing counted by pieces, or by holes in the wall<\/td>\nThree units, triple the product<\/td>\n<\/tr>\n
Flashing, sealant, labor<\/td>\nA strip that diverts water, a compound that fills the joint, and the install work<\/td>\nThe detail that keeps water out<\/td>\n<\/tr>\n
Rough opening<\/td>\nThe unfinished framed opening<\/td>\nOrder against this, not the window<\/td>\n<\/tr>\n
New construction<\/td>\nUnit built into the wall<\/td>\nNo demolition, new builds only<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The Five Term Distinctions That Change What You Pay<\/h2>\n

These five most reliably change the number on the quote.<\/p>\n

What is a good U-factor?<\/strong> At or below 0.30 is a reasonable target, below 0.20 is strong for a cold climate, and anything above 0.35 in a heating region is worth questioning. It depends on your climate zone and frame, which is why the regional ENERGY STAR label beats one number.<\/p>\n

Here is the short version of each one.<\/p>\n

Full-frame or pocket replacement?<\/strong> Full-frame takes out the entire unit, frame and sill included, so the opening can be inspected, flashed, and insulated. Pocket installs a new sash into the frame already there. Full-frame costs more but fixes what is wrong.<\/p>\n

These next two come up on every door quote.<\/p>\n

Do I need tempered glass?<\/strong> In most US residential codes, yes, in all doors and in windows within 24 inches of a bathing fixture, plus many stair and floor-level openings. You will see it on every patio door lite. It is a safety requirement, and a quote that omits it is suspect.<\/p>\n

The third one trips up bedroom buyers.<\/p>\n

What is egress?<\/strong> Egress is code terminology for the means of escape from a room, and the window requirements are specific: minimum clear opening size, minimum sill height, and operable without tools from inside. Bedrooms and basements are where you hit it most, and a window too small stops a sale.<\/p>\n

The last one trips up shoppers reading a spec sheet.<\/p>\n

What does Low-E mean?<\/strong> Low emissivity means the glass surface has a microscopically thin coating that reflects infrared heat while letting visible light through. It keeps heat outside in summer and warmth inside in winter. Low-E is an energy treatment, tempered glass a safety one, and one pane can have both.<\/p>\n

Those five questions come up in nearly every window purchase.<\/p>\n

Next step: get the unit and the install priced separately. The double-hung versus casement comparison<\/a> settles which operation style you want before anyone quotes it, and the installation cost guide<\/a> shows what the labor line should look like.<\/p>\n

For the rest of the picture, the windows and doors guide<\/a> pulls the family together.<\/p>\n<\/article>\n","protected":false},"excerpt":{"rendered":"

Two quotes arrive on your kitchen table, both for the same job, both plausible. One says full-frame replacement, the other says pocket replacement. One lists a U-factor of 0.24, the other calls the same window energy efficient. You cannot tell which deal is better without knowing the words. That vocabulary was written for the supply […]<\/p>\n","protected":false},"author":2,"featured_media":405,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[75],"tags":[95],"class_list":["post-406","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-windows","tag-windows"],"_links":{"self":[{"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/posts\/406","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/comments?post=406"}],"version-history":[{"count":7,"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/posts\/406\/revisions"}],"predecessor-version":[{"id":1365,"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/posts\/406\/revisions\/1365"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/media\/405"}],"wp:attachment":[{"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/media?parent=406"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/categories?post=406"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.skala8.com\/blog\/wp-json\/wp\/v2\/tags?post=406"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}