A scanned room can have a wide variety of windows:
A typical clear or low-e glass window in a wood, vinyl, or metal frame
A high-performance window with an NFRC sticker giving manufacturer-rated U-value and SHGC
A window in a more complex assembly like a bay window or garden window
A window shaded by an architectural overhang, an internal shade, an insect screen, or a sun screen
Windows are the most complex part of Manual J — small changes in any one assumption can produce large swings in heating and cooling loads. Getting the Window settings right is essential to accurate load calculations.
This article walks through every setting on the Window screen.
Always verify construction details and assumptions in the home. Windows are the most complex part of Manual J, so take extra time to verify exactly what kind of windows the home has. The single most sensitive assumption is whether the glass is clear or low-e — this one setting can dramatically affect cooling loads in sunny climates and heating loads in cold climates. See How to determine if you have "low-e" or "clear" windows for how to verify in the field.
Note about window orientation: Amply automatically sets the direction each window is facing based on the iPad's compass when you scan the room. You don't need to set orientation manually — Amply handles it. Just scan each room with the iPad in the actual space.
Edit window assumptions
To make changes to a window, simply tap on the window in the 3D model, and the sidebar will appear where you can edit the assumptions about the glass, frame, and any shading.
Type
Type tells Amply whether you're modeling a window using Manual J's standard generic categories or using manufacturer-rated NFRC values:
Generic — Amply applies Manual J's default U-value and SHGC for the frame, assembly, and glass categories you select below. Use this for most windows where you don't have an NFRC sticker or are unable to find the information using the serial number that is etched into the glass (typically on lower right or left of window).
NFRC Rated — enter the U-value, SHGC, and number of panes directly from the NFRC rating (typically on a label on the window or in the manufacturer's product literature). This is more accurate when the values are available, and is the right choice for high-performance windows where the manufacturer-specified values matter more than the generic defaults.
Which path do the rest of the fields use? When Type is NFRC Rated, the U-value and SHGC are read directly from your inputs, and the Frame, Assembly, and Glass fields below are no longer used in the calculation. When Type is Generic, those fields are how Amply looks up the right Manual J defaults.
Frame and Assembly Type
Frame describes the material and construction of the window frame. The four options correspond to Manual J Table 2A:
Wood or vinyl
Metal w/ thermal break
Metal w/o break
Fiberglass with insulation
Assembly Type describes the geometric configuration of the window:
Flat — a standard window flush in the wall plane.
Bay — a window that projects out from the wall as a multi-panel arrangement. Manual J Table 2A applies a 1.15 surface-area correction to account for the additional glazing on the side panels.
Garden — a fully projecting window, common above kitchen sinks. Manual J applies a 2.75 surface-area correction reflecting the much larger glazing surface relative to the rough opening.
Glass
Glass describes the glazing on the window itself. This section only applies when Type is set to Generic — when Type is NFRC Rated, U-value and SHGC come directly from the NFRC sticker and the glass selections here are not used.
The Glass Type options follow Manual J's categories:
The two most common glass types in homes:
Clear
LowE
Pro tip on how to determine if you have "lowE" or "clear" windows - it's really easy to do and super important
Additional options (rarely used):
Heat absorbing
Reflective
Jalousie
Glass or plastic block
French door
French Door - LowE
The Glass card also includes settings for the number of panes (e.g., 1-pane, 2-pane), whether the window has a storm window installed over it (Has Storm), and the Operability of the sash (e.g., operable or sliding, fixed). Pick the option that matches the actual window — these have intuitive option lists in the dropdowns.
Overhang
Overhang describes any architectural element above the window that shades it from direct sunlight — a roof eave, an upper-story floor, a porch roof, or a built-in awning. Two dimensions describe the geometry:
Overhang Distance— the horizontal projection of the overhang out from the wall, in feet.Top Of Opening To Overhang— the vertical distance from the top of the window opening up to the bottom of the overhang, in feet.
Together these determine the shade line — how much of the window is in shade at different times of day and year.
Overhangs are particularly sensitive at lower US latitudes. In the southern portion of the United States, very small changes in overhang distance produce very large changes in shading. Measure the overhang distance and the top-of-opening distance carefully on site and double-check during your review — guessing at these numbers can swing cooling loads noticeably.
Shading
Shading covers what's blocking or diffusing sunlight at the window beyond the architectural overhang. There are three fields:
Internal Shade— covers blinds, roller shades, and drapes in either fully closed or half-open configurations. Pick the option that matches what's typically installed and used in the home.Shade Color— when an internal shade is selected, this affects how much solar radiation the shade reflects vs absorbs. Lighter colors reflect more.
Insect Screen— describes any insect screen on the window:Full outdoor
Full indoor
Half indoor
Half outdoor
None
Sun Screen Type— describes any dedicated sun screen (a more aggressive solar shading product) installed over the window itself on the exterior of the window.
Insect screens are commonly overlooked by practitioners in the field. A Full outdoor insect screen on an east, west, or south-facing window can reduce solar gain by 20%, so it's important to pay attention to this detail.
Foreground Reflectance
Foreground Reflectance describes what's in front of the window outside (e.g., grass, snow, concrete, water) and how much sunlight it reflects back up into the window. Lighter or shinier surfaces reflect more solar gain into the window than darker surfaces like green grass or asphalt.
Setting a "default" window
Once the window matches a typical configuration in the home (e.g., the main living-area windows), turn on Use as default window. Amply then applies the same settings to every subsequent window you scan. You can always override the default for individual windows that are different - for example, a bay window in the dining room, a window with a permanent sun screen, etc.
