Voids found in house wall during renovation © Daniel FriedmanHow to Set Priorities for Preventing Building Heat Loss

  • HEAT LOSS PREVENTION PRIORITIES - CONTENTS: In what order should we fix drafts, add insulation, tune up heating equipment to save the most on heating cost. How to measure or calculate heat loss (or gain) in a building. How to measure heat transmission in materials: definition of R-values, U-values, K-values, BTU, calorie, and rates of heat loss or gain. Building design temperatures & how to use a home energy audit or heat loss analysis. What insulation "R" values should be used in a building insulation?
  • POST a QUESTION or READ FAQs about the priority of steps to take when cutting heating bills by reducing building heat loss - priority of fixing air leaks, sealing, caulking, insulating, etc.

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This article explains the priorities for preventing heat loss in a building.

We also discuss how to measure or calculate heat loss in a building, defines thermal terms like BTU and calorie, provides measures of heat transmission in materials, gives desired building insulation design data, and shows how to calculate the heat loss in a building with R values or U values.

Our page top photo illustrates a large insulation void in the walls of a building renovated by the author (DF). The seller had informed us that the house was "fully insulated". Our repair of this area is shown below.

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Eight top priorities when working to make a building energy efficient, warm, or cool?

Insulation added to empty wall cavity © Daniel FriedmanOur house renovation wall photo (left) shows how we insulated the wall cavity that had been found vacant (photo at page top) during building renovations.

If we had not had other reasons to strop the walls in this room (loose falling plaster) we'd have considered blowing-in cellulose insluation - leaving the walls more nearly intact.

Watch out: on this and other older homes we renovated I often found voids in "blown-in" insulated walls where installers had not anticipated wall cavity blockages formed by diagonal bracing or fire stopping.

When the object is to make a building more energy efficient, and before any more sophisticated analyses are performed using thermography, insulation evaluations, or even calculations of areas, "R" values, "K" values, or "U" values (defined below), remember this order of concerns when working for building efficiency.

The order of magnitude of sources of un-wanted heat loss in a building are pretty much this:

1 - Close open windows or doors when a building is being heated or cooled by other than "natural means" (like using fans, summer breezes or evaporative coolers in windows). Where older windows are leaking air but are otherwise in good condition, it may be most-economical to install a high quality, well-installed, storm window.

Ceiling fan air leaks © Daniel Friedman

2 - Investigate and cure leaky windows or doors or other openings that are producing drafts; also check for drafty wall or ceiling vent fan openings such as kitchen fans and whole house ceiling exhaust fans that have been left un-covered during the heating season. See BLOWER DOORS & AIR INFILTRATION - how to measure air leaks, equivalent leakage area (ELA), and air changes per hour (ACH) in a building.

Close other obvious building openings where heated air pours out of the structure, such as the whole-house ventilating fan shown in our photo at left.

Watch out: while it makes complete sense to make an insulated cover for the whole house venting fan shown in our photo, if you forget to remove the fan cover before turning this device back on you are inviting a house fire: if fan blades jam the fan cover and stop the motor it may overheat. So don't just throw loose insulating bats over the fan. Some builders construct a lightweight styrofoam cover in hopes that if some fool turns on the fan without removing the cover the fan will blow the cover aside. We like to install a plastic "OFF" lock on the fan switch when a cover is in place.

3 - Top Floor Priorities of placing or improving building insulation: Investigate and make sure that the top floor ceiling or attic floor (or cathedral ceilings) have been insulated, with no insulation voids or areas where insulation was removed or omitted. See INSULATION INSPECTION & IMPROVEMENT

4 - Wall insulation priority: Investigate and consider installing or adding wall insulation.

5 - Building perimeter insulation: investigate and insulate any other un-insulated building perimeter areas such as the building rim joist or band joist accessed from a basement or crawl space.

6 - Insulate under floors over un insulated crawl spaces (we prefer to make the whole crawl space an enclosed and conditioned space).

7 - Insulate building foundation walls below grade in basements or in conditioned-space crawlspaces.

8 - Investigate the efficiency and state of tune of the building's heating or cooling equipment, including boiler or furnace and the condition of the heating or cooling delivery system (baseboards or ductwork, for example). (Warning: have heating systems cleaned and tuned by an expert before accepting a measurement of the system's efficiency.)

How to Really Foul Up a Radiant Heat Concrete Floor Installation - Mistakes to Avoid

The full text version of this article has been relocated to RADIANT HEAT FLOOR MISTAKES where we describe installation specifications for radiant heat flooring in a poured concrete slab along with a detailed report of just how bad a radiant heat floor slab installation can be. The article's conclusions include this insulation advice:

  • Insulate below the floor slab
  • Insulate the slab perimeter, making sure that the insulation design does not rely on foam placed against the slab perimeter and extending above grade up to siding where it will invite termites or carpenter ants into the structure
  • Place the radiant heat tubing at the industry-recommended depth down from the surface of the slab. Typically the maximum depth that tubing should be placed in a concrete floor slab is 2" down from the finished floor surface.
  • If you cannot be present at the job site at critical stages in construction, find someone knowledgeable who can inspect for you before the work continues
  • If your contractor is an opinionated bully, find someone else as soon as possible, even if his or her other work was good.



Continue reading at HEAT LOSS R U & K VALUE CALCULATION or select a topic from the More Reading links shown below.


Or see HEAT LOSS INDICATORS - where is the building losing heat during the heating season, or gaining un-wanted heat during the cooling season

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HEAT LOSS PREVENTION PRIORITIES at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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