A wall in a scanned home can fall into several different categories, and each is treated differently in the load calculation:
Exterior wall (exposed to outdoor air)
Partition wall (against a buffer space like an attached garage)
Below grade wall (2 or more feet below outdoor grade)
Interior wall (between two conditioned rooms - no load)
Manual J only calculates a load on walls that are exposed to temperatures different from indoor living conditions, so classifying each wall correctly matters as much as getting its construction right.
This article walks through every setting on the Walls screen.
Always verify construction details and assumptions in the home. Note any R-value labels visible on the face of cavity insulation, or use your professional judgment based on the type of insulation, the stud depth, and any continuous board insulation.
When in working in an older home, that has 2x4 construction, we strongly recommend verifying the presence (or absence) of insulation by:
Safely removing an outlet cover
Probe, using a non-conductive tool (or do simple visual inspection), around the junction box
Note about "Is Exterior": Loads are only calculated on walls that are considered exterior — walls exposed to temperatures higher or lower than typical indoor living conditions. Interior walls between two conditioned rooms are not counted.
Amply automatically marks a wall as exterior if it has a window in it
You can also set it manually with the "Is Exterior" toggle in the upper right of the sidebar when a wall is selected
Partition walls: A wall can also sit against a partition space - an area that is neither at outdoor temperature nor equal to indoor conditions. The most common partition is a wall shared with an attached garage. Mark these by tapping the Is Garage Partition toggle so Amply uses the buffered garage temperature instead of the outdoor design temperature.
Below grade walls: If a wall is 2 or more feet below grade, mark it as is below grade. See below grade walls - verify and edit for the details.
Edit wall assumptions
To make changes to a wall, tap on the wall in the 3D model, and the sidebar will appear where you can edit its assumptions — whether it's exterior, a garage partition, or below grade, along with all the details of the wall construction.
Then tap on any assumption menu to make changes. In the example below, you would tap on Construction to change the wall type.
Construction
Construction tells Amply what the wall is built from. Pick the option that matches what is actually there:
Frame: Wood or metal studs with insulation in the cavity. The most common above-grade residential wall.
Block: Concrete masonry (CMU) wall aka cinder block, with open or filled cores and optional board insulation.
Log Wall: Solid stacked-log wall, where the wood mass itself is the thermal barrier.
Structural Foam Panel: A structural insulated panel (SIP): a foam core bonded between two structural facings.
Autoclaved Aerated Concrete: Lightweight precast aerated concrete block (AAC).
Insulated Concrete Form: Concrete poured between two layers of rigid foam (ICF).
8" Brick or Concrete: A solid 8-inch masonry or concrete wall.
4" Concrete: A solid 4-inch concrete wall.
The remaining fields below describe a Frame wall. For mass walls (block, concrete, AAC, ICF, and similar), the construction itself defines the assembly, so the framing fields may not apply. However, it is common for masonry walls to have interior studs and insulation, so verify if that is the scenario you're working with and reflect that in your wall assembly assumptions.
Stud Size
Stud Size sets the depth of the wall cavity for a framed wall — for example 2x6 — which determines how much cavity insulation can fit. Match it to the actual framing where you can see it (an exposed rim joist, an attic kneewall, or an unfinished section) or verify by measuring the depth of the wall at an exterior door opening or window opening.
Stud Material
Stud Material is whether the studs are Wood or metal. Metal studs conduct more heat than wood (thermal bridging through the framing), which Amply accounts for in the wall's overall assembly performance.
Cavity Insulation
Cavity Insulation is the R-value of insulation between the studs — for example R19. Note the value from a label on the insulation face if it's visible, or use your professional judgment based on the insulation type and the stud depth. Most walls that are 2x6 have a minimum of R19 insulation.
Board Insulation
Board Insulation is continuous rigid insulation applied across the wall — typically exterior foam sheathing — which adds R-value on top of the cavity insulation and reduce thermal bridging by studs. Set it to None when there is no continuous board insulation.
Exterior Finish
Exterior Finish is the wall's cladding, such as Siding/Stucco or brick veneer. It describes the outer surface of the assembly.
Handling more exotic wall assemblies
The Manual J standard does not account for all possible wall assemblies that may be observed in the field. If you are finding that you don't see an option for a combination of assumptions that match a wall assembly you're trying to model, it is okay to identify or use a wall assembly that is the closest overall U-value of that entire wall assembly. You can see the calculated U-factor in the lower right of the sidebar for any wall assembly.
U-factor = 1 / R-value of wall assembly
Set your changes as the default
Once a wall matches the typical above-grade wall construction of the home, turn on Use as default above grade wall. Amply then applies the same settings to every subsequent above-grade wall you scan. To push the configuration to every above-grade wall in the current room at once, use Apply to all above grade walls in this room. Override either one for individual walls that are built differently.