Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
INSULATION INSPECTION & IMPROVEMENT
ACOUSTICAL SEALANT CHOICES
AIR LEAK MINIMIZATION
ASBESTOS IDENTIFICATION IN BUILDINGS
BASEMENT CEILING VAPOR BARRIER
BASEMENT HEAT LOSS
BRICK LINED WALLS
BRICK VENEER WALL AIR LEAKS
BUCKLED FOUNDATIONS due to INSULATION?
CATHEDRAL CEILING INSULATION
CATHEDRAL CEILING VENTILATION
CEILINGS, DROP or SUSPENDED PANEL
DEW POINT TABLE - CONDENSATION POINT
DUCT INSULATION, ASBESTOS PAPER
FIBERGLASS PARTICLE CONTAMINATION
Fiberboard Insulation Sheathing Mold
FIBERGLASS INSULATION MOLD
FIREPROOFING ASBESTOS SPRAY-ON
FRAMING DETAILS for BETTER INSULATION
FRAMING DETAILS for DOUBLE WALL HOUSES
FRAMING METAL STUD PERFORMANCE
FREEZE-PROOF A BUILDING
HEAT LOSS in BUILDINGS
HEAT LOSS PREVENTION PRIORITIES
HEAT LOSS R U & K VALUE CALCULATION
HOUSEWRAP AIR & VAPOR BARRIERS
HOUSE DOCTOR, how-to be
HUMIDITY LEVEL TARGET
ICE DAM PREVENTION
INSULATION AIR & HEAT LEAKS
INDOOR AIR QUALITY & HOUSE TIGHTNESS
INSULATION FACT SHEET- DOE
INSULATION IDENTIFICATION GUIDE
INSULATION INSPECTION & IMPROVEMENT
INSULATION LOCATION - WHERE TO PUT IT
INSULATION R-Values & Properties
LEED GREEN BUILDING CERTIFICATION
LOG HOME ENERGY EFFICIENCY
MOLD in FOAM INSULATION, RESISTANCE
MOISTURE CONTROL in BUILDINGS
NOISE / SOUND DIAGNOSIS & CURE
RIGID FOAM USE INDOORS
SHEATHING, FOIL FACED - VENTS
SLAB INSULATION, PASSIVE SOLAR
STAINS on & in BUILDINGS, CAUSES & CURES
STRAW BALE CONSTRUCTION
STUCCO WALL METHODS & INSTALLATION
STUCCO OVER FOAM INSULATION
SWEATING (CONDENSATION) on PIPES, TANKS
Thermal Expansion Cracking of Brick
THERMAL IMAGING, THERMOGRAPHY
THERMAL MASS in BUILDINGS
THERMAL TRACKING Indicates Heat Loss
TRUSS UPLIFT, ROOF
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VENTILATION in BUILDINGS
WALL CONSTRUCTION BARRIER vs CAVITY
WIND WASHING INSULATION At EAVES
WINTERIZE A BUILDING
This article provides a Table of Insulation Values and Properties for Various Insulation Materials useful in procedures to measure or calculate heat loss in a building, defines thermal terms like BTU and calorie, provides measures of heat transmission in materials, building insulation design data, and heat loss in a building. Page top photo by the author. Formula-R and Owens Corning which may be visible in this photograph of pink Styrofoam insulation boards are registered trademarks of Owens Corning and were photographed at a Home Depot® building supply center.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved.
Table of Characteristics of Various Insulating Materials: fiberglass, mineral wool, cellulose, foam insulating board, UFFI, vermiculite, others
Because no amount of insulation can keep a drafty building warm, also review ENERGY SAVINGS PRIORITIES. See BLOWER DOORS & AIR INFILTRATION for a discussion of measuring air leakage in buildings. Also see HEAT LOSS INDICATORS (where is the building losing heat during the heating season, or gaining un-wanted heat during the cooling season), and see HEAT LOSS R U & K VALUE CALCULATION for a guide to calculating heat loss (or gain) rates for buildings and building insulation.
Notes to the Table of Building Insulation Properties
Frequently Asked Questions (FAQs) about the R-values and insulating properties of various materials
Reply: Earth or soil has an R-value of about R 0.25 to R-1.0 per inch at 20% moisture content and other assumptions discussed here
But really, the insulating value of earth depends .... as we elaborate below. Also see "Dirt" in our table of insulating values shown just above
Sketch at left, courtesy of Carson Dunlop Associates, illustrates the effects of soil density and moisture as a source of pressure on a foundation wall.
As we note below, the R-value of the wet soil (sketch center) will be much lower than dry soil outside of the same volume of dry soil (sketch left). Freezing at the upper level of such wet soil also will affect its heat transfer rate as well as risking foundation damage as we show here.
Some sources we researched assert that "one inch of 'insulation' is equal to about two feet or more of soil. If we take 'insulation' to be a bit more specific, say the most commonly-used material, fiberglass, that's about R3 /inch for fiberglass, or if we believed the soil R-value rule of thumb about dirt, that's about 24/ 3 = about R 0.8 for arbitrary "dirt" insulation value.
R 0.8 sounds pretty reasonable if we assume about 20% moisture content, and if we consider for comparison or a "sanity check" that the R-value of uninsulated concrete is about R 0.8/inch. Other engineering sources cite the R-value of earth as about R 0.25 per inch. Without normalizing for soil properties and moisture content, these numbers are very arm-waving rules of thumb.
But really this is in my opinion a very unreliable figure given the discussion below about the effects on heat transfer of soil properties and soil moisture. Heck even snow does better, at about R1/inch. In addition to avoiding the confusion that comes from an unreliable R-value for earth (take R 0.25 if you like), discussions of earth berm housing and underground housing usually consider the effects of thermal mass on building comfort, not just R-values.
R-values measure resistance to heat flow or transfer between materials. But thermal mass considers the storage effects of the mass of soil (or concrete block or ?) or other materials that comprise and surround a building. Thermal mass stores heat and returns it during cooler periods, evening out swings in building temperature. So let's keep in mind that while the R-value of two feet of soil outside of a building wall, say, may be R 0.5, that 24" of dirt has much greater thermal mass than the same quantity (in equivalent R-vale) of an insulating material such as fiberglass or solid foam insulation.
What all of this means is that it is a mistake to try to equate thermal mass and insulating values, and it makes no sense to forget about heat flow rates in or out of a structure if you are paying to heat or cool a building.
The R-value of earth depends on the type of soil and its water content. Even more significant can be the movement of groundwater through the surrounding soil, as moving water will significantly increase the rate of heat transfer from warm to cool areas.
At least important to anyone asking this question will be the assumptions about
The soil temperature Ts at some depth where it is stable (such as below the frost line in a freezing climate, perhaps as deep as 20 feet. A Journal of Light Construction online forum discussion of soil insulating properties includes the observation that
" [earth provides a ] huge amount of thermal mass, and that's what you'll be working with or fighting against. The soil temperature at about 20' is equal to the year round ambient temperature, so that will tell you what you'll be working with/against. If you want the room warmer or cooler than that, it's easier to install insulation and create a thermal mass inside that insulated envelope, if the ambient temperature is close to what you want, well, you don't need heat."
For a more scholarly discussion of the insulating properties of soil you should consult a heat transfer engineer or a soils engineer. But here are my views of some important parameters to consider when assigning an insulating value to soil:
Material I've reviewed about earth sheltered homes and schemes that use electric radiant heated floors over uninsulated soil (where electricity is dirt cheap), but I'd prefer to evaluate that "design" with comments by heat transfer experts since it seems to me that any system that pumps heat into uninsulated ground in a cold climate is spending a significant portion of their heating dollar to return heat to Mother Earth rather than to Mommy upstairs.
The claim that "heat you pump into the ground under or around a home doesn't really go anywhere" is in violation of the basic laws of thermodynamics and is simply not so. Heat flows from warmer to cooler materials. Sure we can expect there to be a temperature gradient in cool soil beneath or against a heated building, but heat flows from warmer to cooler materials, it doesn't magically stop dead at some arbitrary distance. Just where energy costs are very low and are expected to stay low might it sound plausible to use uninsulated earth for heat storage under or around a building.
hello, just noticed that your insulation value for dirt is inaccurate. if you are saying that 24inches of earth insulates the same as 1 inch of fiberglass, or R3, than that means 8 inches of dirt has R1, or that an inch of dirt is R 0.125. Am i wrong? Cheers, - G.R. 2/29/2013
In this article, just above, we include a longer discussion of this question about the insulating properties of soil or dirt.
In fact there is no single right soil R-value answer without considering soil moisture levels and soil density, particle composition, but our research did find some interesting scholarly articles that gave a range of values. Above we give quite a few source citations on this topic.
In sum, if you like a dir R-value of R=0.25 per inch of soil, then 24-inches of dirt at that R-value and moisture assumptions would be about (0.25 x 24 = 6) or R-6.
Questions & answers or comments about the insulating properties of various materials
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Related Topics, found near the top of this page suggest articles closely related to this one.