Energy-efficient house vs. code house: cost, savings and comfort
Configure a new home on your Front Range land and compare it with a house built to Colorado's current energy code: what each choice costs to build, what it saves on energy, and how much more comfortable it is to live in. Upgrades are priced at builder cost: extra material and labor, no markup.
- 100% free
- No email needed
- Nothing you enter leaves your browser
Where the heat goes
Yearly heat loss by part of the house, before sun and internal gains make up some of it.
- Walls
- Roof
- Windows & doors
- Slab
- Air leaks & ventilation
- Corners & junctions
Heat needed by month
What the heating system has to supply after sun through windows and household heat. With hydronic solar, the collectors' share is shown separately.
- Code house
- Your house, from collectors
- Your house, from heating system
Living comfort
How the house feels to live in, scored 0–100 from your choices: surface temperatures, drafts, fresh air, steadiness, humidity and noise. A relative index for comparing designs, not a measured standard.
- Code house
- Your house
Edit unit costs
Priced as BuildAtPeace building it: only the extra material and extra labor, at cost, no markup. Labor hours are multiplied by the labor rate. Heating and cooling equipment uses typical subcontractor pricing. 2026 Front Range estimates; replace any number with your own and every result updates.
How this is calculated
- Code house: built to the Colorado Model Low Energy and Carbon Code (2024 IECC basis), Climate Zone 5 above 4,000 ft: walls U-0.045, ceiling U-0.024, windows U-0.30, R-10 slab edge, 3.0 ACH50, exhaust ventilation, L-shaped plan, windows spread evenly, gas furnace. Some jurisdictions still enforce the 2021 IECC, and the new code also requires extra efficiency credits that aren't modeled, so a real code house may be slightly better than this.
- Geometry: floor area and stories set the footprint. Shape sets perimeter, roof surface, corners and how hard the house is to seal. The golden section is a 1.618 : 1 rectangle. Slab-on-grade, 9 ft ceilings. Curb appeal (porch, entry gable, trim and siding accents) is outside the heated space and doesn't change energy use.
- Building types: wall U-factors are whole-wall values including framing. Perfect Wall, ICF and SIP cut corner and junction losses and make air sealing cheaper; ICF adds some thermal mass. SIP walls come in panel thicknesses.
- Heating: monthly heat balance for Denver (NOAA 1991–2020 temperatures, approximate NREL solar on vertical and 55°-tilted surfaces), split into cold, cloudy days and typical sunny days, with ISO 13790 gain use scaled by thermal mass. Screening model, not a certified HERS or Phius model.
- Orientation: turning the main glass wall east or west moves its winter sun toward east/west values. West-facing glass adds summer afternoon heat; east-facing adds a little less. Glass on that wall is capped at 60% of the wall.
- Cooling: degree-day estimate plus summer sun. Equipment is sized from design heat loss at 1°F outside and from peak cooling load.
- Hydronic solar: flat-plate collectors at about 55° tilt, 42% average useful efficiency after storage and piping losses, covering at most 85% of any month's space heat. Collector output left over also preheats domestic hot water (up to 75% of it), credited at the backup's fuel cost. Collectors, storage and radiant floors are priced at builder cost; radiant floors replace ductwork. The default collector size covers about 70% of the house's heating plus hot water. Cooling by ductless mini-splits.
- Prices (Oct 2026): Xcel gas ≈ $1.05/therm all-in, Colorado electricity 17.1¢/kWh (EIA, June 2026), 30-yr fixed ≈ 7.28% (Freddie Mac, Oct 1, 2026). Water heating, cooking, lights and plug loads are the same for both houses and left out, as is the gas meter charge.
- Money: everything is shown per month compared with the code house. The mortgage share of the up-front difference is paid over the loan term at your rate; the cash share paid at closing shows as lost investment earnings at your return rate. Property tax and insurance on the added cost, upkeep, and the equipment set-aside rise 3% a year; energy savings rise with your energy price increase. Heating and cooling equipment is replaced at the end of its life, and its cost is spread over that life as a monthly set-aside. Your equipment lasts longer the fewer hours it runs (up to 35% longer); heat pumps run year-round and are assumed to last 15% less. Collectors and radiant tubing outlast the 30-year window. HRVs and ERVs add $100/yr upkeep, solar thermal $250/yr. The 30-year comparison carries every dollar (cash at closing, each month's extra costs, each month's energy savings) at your return rate, compounded monthly; lost earnings are not counted again there because compounding the cash already includes them.
- Living comfort index: six weighted parts (even temperatures 25%, drafts 20%, air quality 20%, steady temperatures 15%, humidity 10%, quiet 10%). Surface temperatures are calculated for a 10°F night with 68°F inside; the other parts score airtightness, ventilation type, thermal mass, overheating risk, heating system and wall and window type. It is a relative index for comparing designs, not a measured or certified standard.
- Incentives: the federal 45L credit ended June 30, 2026. Xcel's new-home program pays $20k or more for qualifying homes with no gas service.
About these numbers
EnergyComfortCalc gives planning-level estimates to help you compare design choices. It is not a construction quote, an energy audit, or engineering, financial, tax or legal advice. It prices only the differences from a code-built house; for a detailed estimate of what the whole house will cost to build, use the Guesstimator.
Up-front costs assume BuildAtPeace builds the house and charges only the extra material and labor at cost; another builder's prices will differ. Results come from a simplified monthly energy model, average Denver-area weather and typical 2026 Front Range costs and utility prices. Your actual building costs, energy use and savings will differ, sometimes by a lot, depending on your design, site, builder, workmanship, how you live in the house, future weather, and future energy prices and interest rates.
Before you make decisions, confirm the numbers with a certified energy rater (HERS or Phius), a heating and cooling load calculation (Manual J), your builder's pricing, and your lender or tax professional. Rebates and incentives change often and have eligibility rules; check the program's current terms before counting on one.
The living comfort index is a relative score for comparing designs, built from the factors described under "How this is calculated." It is not a measured or certified comfort rating, and how comfortable a home feels also depends on things this tool can't see.
BuildAtPeace and Epic Structure LLC make no warranty that these results are accurate or complete, and are not liable for decisions made based on them.