# Room Heat Loss Calculator — United States

> Estimate steady-state room heat loss from entered fabric properties, air exchange and a local outdoor design temperature. USD planning view; stated limitations apply.

Page: https://askcalculators.com/us/heat-loss/
Definition: https://askcalculators.com/us/heat-loss/definition.json
JSON Schema: https://askcalculators.com/us/heat-loss/schema.json
Version: 20.16.0
Maintained by: AskCalculators (software project; not a credentialed reviewer)
Qualified review: pending. Automated checks do not establish professional approval.
Page status: Live
Review status: Pending

## Use
Open the calculator page and enter values. Query-string parameters can restore and bookmark a calculation.
Example: https://askcalculators.com/us/heat-loss/?unitSystem=imperial&wallArea=538.195520835486&wallU=0.05283305514296545&roofArea=430.55641666838886&roofU=0.035222036761976966&windowArea=86.11128333367778&windowU=0.24655425733383876&floorArea=430.55641666838886&floorU=0.04402754595247121&volume=3531.466672148859&airChanges=0.5&insideTemp=68&outsideTemp=23

## Inputs
- unitSystem: Measurement system; type=select; optional; default=imperial; values=imperial|metric
- wallArea: Exposed opaque wall area; type=number; required; default=538.195520835486; min=0; max=10763910416709.72
- wallU: Wall U-value; type=number; required; default=0.05283305514296545; min=0.0017611018380988483; max=1.7611018380988483
- roofArea: Exposed roof area; type=number; required; default=430.55641666838886; min=0; max=10763910416709.72
- roofU: Roof U-value; type=number; required; default=0.035222036761976966; min=0.0017611018380988483; max=1.7611018380988483
- windowArea: Window and external door area; type=number; required; default=86.11128333367778; min=0; max=10763910416709.72
- windowU: Window/door U-value; type=number; required; default=0.24655425733383876; min=0.0017611018380988483; max=3.5222036761976967
- floorArea: Exposed floor area; type=number; required; default=430.55641666838886; min=0; max=10763910416709.72
- floorU: Floor U-value; type=number; required; default=0.04402754595247121; min=0.0017611018380988483; max=1.7611018380988483
- volume: Heated internal volume; type=number; required; default=3531.466672148859; min=0; max=35314666721488.586
- airChanges: Air changes per hour; type=number; required; default=0.5; min=0; max=20
- insideTemp: Indoor design temperature; type=number; required; default=68; min=14; max=104
- outsideTemp: Outdoor design temperature; type=number; required; default=23; min=-112; max=104

## Outputs
- fabricLoss: Fabric design heat loss; format=number
- ventilationLoss: Ventilation design heat loss; format=number
- totalLoss: Total screening heat loss; format=number; primary

## Formula
heat loss, W = Σ(area × U-value × temperature difference) + 0.33 × air changes × room volume × temperature difference.

Inputs are converted to canonical units before evaluating this stated formula.

## Rules
- Empty optional inputs are undefined, not zero.
- Hidden conditional inputs are ignored.
- Do not invent missing required inputs.

Notice: Illustrative defaults are not local quotes or verified legal rules. Dated reference components and user-entered assumptions are explicitly distinguished. Professional review is pending.