The calculator will provide the User with estimated costs and savings that are related to home efficiency investments and regional variation of climate and costs.
The calculator is based upon:
- Minimal input by the User that will generate immediate and useful numeric results.
- The howmuch.net regional data base, its programing, and related Cost Guide products.
- The correct application of technical, commercial, and economic formulas.
Ceiling insulation upgrade calculator
The subject of home insulation is rich in science regarding heat transfer and the variation of regional climate and installed cost. Gratefully, the home insulation sector is highly commercialized in common terms for comparison; and it is highly supported by related national and regional governmental agencies.
Calculator theory of operation
The calculator Output is based upon a linear approximation of insulation rating upgrade (from low-or-no ceiling insulation to ASHRAE Zone recommended R-value) versus expected heat flow reduction and the proportional annual heating and cooling bill reduction.
The User is requested to input three numeric values:
- Their zip code which is used directly to access howmuch.net cost information and variability of both materials and labor to complete the installation or service; and indirectly by association to ASHRAE Zones 1 through 8.
- The floor plan-area of all conditioned spaces (square feet).
- The typical annual heating and cooling bill ($/year).
The User is immediately provided with estimated cost and savings numeric values Output.
The accuracy of the savings estimate is estimated to be within +/- 18% of true value. Additional annual variation of +/- 15% due to ordinary climatic variation is not considered.
The cost estimate of the home improvement investment is calculated using the howmuch.net data base of Cost Guides that provide typical national cost values (material and labor) that are further adjusted for regional variations per zip code (http://www.fixr.com/info/map.html ).
Labor cost varies from about 10% less to 50% more than the national typical value. Boston, San Francisco, and New York City are examples at the high end of that variability. Material costs have less variation, from 10% less to 20% more than the national typical value.
Key attributes of the ceiling insulation upgrade calculator
- The random variable of the statistical distribution is “SAVINGS” that proportions linearly the User Input heating and cooling bill to the regional estimation of savings-rate.
- SAVINGS analysis takes into account:
- the proportion of heating and cooling bill applicable to just the ceiling component
- regional variation of energy costs and climate demands that are intrinsic to the User Input heating and cooling bill
- the diminishing returns of savings versus cost of additional insulation.
- The home is occupied by two adults and two children less than 15 years of age.
- Cooling is done by electric means; heating may be as well, or by natural gas regionally.
- All spaces of the floor plan area are conditioned for both heating and cooling.
- All other energy efficiency measures are in place in the home, only the ceiling part of the building is considered which may include the interior roof surface.
- The upgrade starting point at R-2 takes into account the insulating value of a typical wood house ceiling and roof structure without any insulation in place.
- The insulation upgrade calculator does not evaluate collateral draft-sealing or sound-deadening effects that may increase comfort in the home, though both may be results of insulation upgrade.
Known limitations
- Cost values do not include taxes, fees, or other administrative costs or benefits of subsidy.
- The interaction of home energy efficiency measures is complex; the estimation of savings would be less if other measures are not in place.
- This calculator is calibrated in August of 2015; subsequent market changes in should alert the User to proportional changes in calculator Savings evaluation.
Release History
August 1st, 2015: web-publication of ceiling insulation upgrade scenario calculation.
Feedback & Questions
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Documentation
ASHRAE R-Value Climate Zone Map
Figure 1: ASHRAE R-Value Climate Zone Map
|
Zone: |
1 |
2 |
3 |
4 - 4M |
5 + 4M |
6 |
7 & 8 |
|
R_ceiling: |
R-20 |
R-25 |
R-25 |
R-30 |
R-30 |
R-30 |
R-35 |
Insulation Rating Upgrade versus Heat Flow Reduction
The diminishing return of additional insulation costs versus heating and cooling bill savings can be demonstrated in terms of heat flow reduction.
Figure 2: Insulation Rating Upgrade versus Heat Flow Reduction
Cost
| R | 20 | 25 | 30 | 35 |
| Total Cost ($/SF) | $1.286 | $1.336 | $1.416 | $1.516 |
| Labor Cost ($/SF) | $0.416 | $0.416 | $0.416 | $0.416 |
| Material Cost ($/SF) | $0.870 | $0.920 | $1.000 | $1.100 |
| Man hours per | 0.013 | 0.013 | 0.013 | 0.013 |
| Hourly rate | $32 | $32 | $32 | $32 |
Look-up Table
| ASHRAE Zone | R-value | Cost Ceiling | Saving Ceiling |
| 1 | R-20 | $1.29 | 29.2% |
| 2 | R-25 | $1.34 | 46.3% |
| 3 | R-25 | $1.34 | 44.6% |
| 4 | R-30 | $1.42 | 46.7% |
| 5 | R-30 | $1.42 | 46.5% |
| 6 | R-30 | $.142 | 38.5% |
| 7 | R-35 | $1.52 | 38.0% |
| 8 | R-35 | $1.52 | 38.0% |
Calculator Fields
- Inputs:
- User's zipcode must be translated to ASHRAE Zone
- Square Feet of building
- Annual heating and cooling bill
- Outputs:
- Cost of ceiling insluation upgrade (plus taxes and fees, minus rebates)
- Typical savings due to the upgrade over ten years (if all other energy issues are covered)
About the article
Authors
Irena - Editor
