As long as I'm here, I was just considering building a cordwood home, or possibly a "sory of " log house. Being a builder, and having studied physics and alternative energy, I ASSUME that cedar (and redwood, and sugar pine, for that matter), being less dense, would have a higher R value. So far, I have never found a CREDIBLE source of R values for different wood species. I only find numbers like "R value for wood = 1.00-1.25"

Anyone have a good source for this info?

Thanks in advance,

JOJ

-- jumpoff joe (jumpoff@ecoweb.net), October 12, 2001

Answers

JOJ...SO YOU SEE THERE IS NOTHING DEFINATIVE ABOUT R-VALUES.

CORDWOODGUY

-- CORDWOODGUY (cordwoodguy@n2teaching.com), October 15, 2001.

JOJ...YES JOE THERE IS A REAL DELEMA ABOUT ACTUAL WOODS R-VALUES

MOST BOOKS PUBLISHED WITH THE R-VALUES USED BY ENGINEERS/ARCHITECTS AND OF COURSE THE GUY YOU HAVE TO DEAL WITH...THE DREADED BUILDING INSPECTOR.

THESE BOOKS CAME OUT IN THE 1950`S AND GIVE AN R=1.0 TO R=1.25 PER INCH FOR SOFTWOODS.

MORE CURRENT ENGINEERING BOOKS GET UP TO R=1.5

I HAVE A STAMPED REPORT FROM EASTERN FOREST PRODUCTS LABORATORY FROM 1978.[EFPL-6-3-307...IT HAS BEEN SAID THAT THIS REPORT DOESN`T EXIST.BUT I HAVE A STAMPED COPY INFRONT OF ME RIGHT NOW.AND A COPY OF IT APPEARED IN ISSUE 6 OF "CANADIAN LOG BUILDING"] THEY DID MORE ACCURATE TESTING WITH MORE MODERN EQUIPMENT AND ACTUALLY MONITORED A LOG HOUSE AND FOUND A MOST REMARKABLE DISCOVERY.THEY FOUND AS THE TEMPERATURE WENT DOWN THE R-VALUE OF WOOD ACTUALLY WENT UP.THEY GAVE WHITE PINE AN R=2.0 PER INCH.THE REPORT WAS USED TO DEFEAT A BUILDING INSPECTOR IN MANITOBA WHO WOULDN`T ALLOW A LOG BUILDING TO BE BUILT BECAUSE IT DIDN`T HAVE ENOUGH INSULATION IN THE WALL.THE CANADIAN LOG BUILDING ASSOCIATION REQUESTED THE TESTS.SEEING AS THERE ARE LOG HOME KITS BEING SOLD ALL OVER THE WORLD NOW.ITS SAFE TO ASSUME THEY MEET CODE.

SEIRRA LOG HOMES PUBLISHED A REPORT BY THE NATIONAL ASSOCIATION OF HOME BUILDERS AND IN CONJUCTION WITH HUD.REPORT NO.2132 DATED APRIL 5TH,1991.OVERALL IT SHOWS THAT LOG HOMES OUT PERFORM STICK BUILT HOMES.

THE REPORT CAN BE FOUND AT THIS URL http://www.pragozd.si/report.htm

HOWEVER,ON THE SIERRA PAGE THEY INCLUDED FIGURES AS FOLLOWS. I`VE CONTACTED NAHB TO SEE IF THEY AGREE WITH THESE FIGURES AND IF THEY INDEED ARE THE SOURCE.THESE ARE ALL PER INCH OF THE FOLLOWING WOODS.[THEY FACTOR IN R-VALUE WITH THERMAL MASS ALLOWANCES]

CEDAR...R=3.78 DOUGLAS FIR...R=3.0 LARCH...R=3.00 HEMLOCK...R=3.58 FIR...R=3.58 SPRUCE...R=3.58 PINE...R=3.58 REDWOOD...R=3.75 SOUTHERN PINE...R=2.76

BECAUSE OF THE THERMAL MASS IN LOG HOMES AND CORDWOOD.THEY RETAIN HEAT AND ARE ENERGY EFFICIENT IF BUILT PROPERLY.

ALSO THE R=VALUES AREN`T JUST CONFUSING WITH WOOD.I HAVE SEEN PUBLISHED REPORTS ON STRAW BALE WALLS UTILIZING 23" BALES.

EBN SAYS R=1.45 PER INCH JOE SAYS R=2.38 PER INCH[1993] SANDIA SAYS R=2.67 PER INCH OAK RIDGE SAYS R=0.94 PER INCH[1998] CEC/ATI SAYS R=1.13 PER INCH[1997] OAK RIDGE SAYS R=1.45 PER INCH[1998]

THERE IS A BIG DIFFERENCE BETWEEN R=O.94 AND R=2.76

SO JOJ...THERE DOESN`T APPEAR TO BE ANY REAL CREDIBLE SOURCE FOR R-VALUES ON ANY MATERIAL.THESE STRAW BALE TESTS ALSO TESTED STICK FRAME HOUSES AND THEY ACTUALLY FELL FAR SHORT OF THEIR SUPPOSED R- VALUES.[R-20 RATED WALLS WOULD TEST OUT AT ABOUT AN R=12]

BUT ALL PEOPLE LIVING IN LOG HOMES KNOW OF THE EFFICIENCY OF A PROPERLY BUILT HOME.THE THERMAL MASS EFFECT FACTORS INTO IT. A LOG BUILDER FRIEND OF MINE TOLD ME HE`S LEFT HIS CABIN FOR SEVERAL DAYS IN COLD WEATHER .RETURNING TO FIND IT STILL SLIGHTLY WARM WHEN THE FIRE WAS OUT WHOLE TIME.THIS IS THE REASON THE LOG BUILDERS REQUESTED THE TESTS BECAUSE THEY FOUND THEY WEREN`T GETTING WHAT WAS DUE.SOME CORDWOOD OWNERS REPORT THAT SOME TIMES IN THE WINTER THEIR FURNACES DON`T COME ON FOR DAYS.I KNOW OF PEOPLE IN A CORDWOOD THAT USE THEIR WOOD STOVE IN THE HOTTEST PART OF SUMMER TO WARM THEIR HOUSE.I`M ALSO AWARE OF PIG BARNS BUILT OF CORDWOOD THAT MAINTAIN 60- 70 DEGREE TEMPERATURES WITH NO HEAT SOURCE OTHER THAN THE PIGS BODY HEAT IN THE WINTER.

THERE WAS ALSO A BOOK PUT OUT AFTER THE RESULTS FROM.LANDMARK ENERGY TESTS DONE BY THE NATIONAL BUREAU OF STANDARDS.I HAVEN`T READ IT BUT IT WAS POSSITIVE TOWARDS LOG HOME R-VALUES.

THE ENERGY ECONOMICS AND THERMAL PERFORMANCES OF LOG HOMES BY:DORIS MUIR AND PAT OSBORNE PUBLISHED BY:MUIR PUBLUISHING

NOW THERE HAVE BEEN REPORTS THAT THERE IS A DIFFERENCE BETWEEN SIDE GRAIN AND END GRAIN R=VALUES OF WOOD.I DISCUSSED THIS WITH AN ENERGY EXPERT AND HE SAYS THAT THE DIFFERENCE IS SO SLIGHT THAT ITS NOT WORTH FACTORING IN.

JOJ...YOU ARE RIGHT ON THE MONEY WITH LESS DENSE WOODS HAVING MORE R-VALUE.THERE DEFINATELY IS A RELATIONSHIP BETWEEN DENSITY AND INSULATION PROPERTIES.

SO WITH NO DEFINATIVE R-VALUES PEOPLE WILL HAVE TO JUDGE FOR THEM SELVES.BUT A CORDWOOD CAN EASILY BE BUILT TO HAVE AN R=60 TO R=100 WALL.MOSITURE CAN PASS THROUGH A CORDWOOD WALL WITH OUT GETTING THE LOGS WET.LOGS BREATH AND MOISTURE PERMIATES FROM A HIGH HUMID AREA TO A LOWER HUMID AREA.BECAUSE OF THEIR MASS THEY ARE ALSO MORE SOUND PROOF.PEOPLE HAVE TRIED TO BURN CORDWOOD HOMES AND FOREST FIRES HAVE BEEN UNABLE TO DESTROY THEM.ALL THE ONES I KNOW OF CAN BE REBUILT AS THE MORTARED WALLS STAY INTACT.BUT NEW ROOFS AND INTERIOR WALLS WOULD HAVE TO BE REBUILT.

SO WHAT OTHER TYPE OF STRUCTURE CAN LAST 1000 YEARS.CAN`T BE BURNT. HANDLES MOISTURE PROBLEMS NATURALLY.THATS ENERGY EFFICIENT.THAT REQUIRES HARDLY ANY SKILLS TO BUILD.PLUS IS VERY ECOLOGICALY SOUND. PLUS COSTS ABOUT 25%-50% LESS THAN CONVENTIONAL CONSTRUCTION.REQUIRES VERY LITTLE MAINTENANCE.

LONG LOG BUILDING REQUIRES TRAINING AND SPECIAL SKILLS.YOU WOULD HAVE TO ALLOW FOR SETTLEMENT.KNOW ABOUT HAZARDS ABOUT USING SPIRAL GRAIN LOGS.HOW TO KNOTCH AND SCRIBE THE LOGS TO FIT.HOW AND WHEN TO FELL AND SEASON THE LOGS.HOW TO LOCALIZE AND CONTROL CHECKING. HOW TO TREAT THEM FROM INSECTS,UV RAYS AND ROT.

GO TO MY CORDWOOD NEWBEE PAGE IF YOU WANT TO LEAN THE BASICS OF CORDWOOD CONSTRUCTION. http://maxpages.com/cordwood

CORDially YOURS CORDWOODGUY

PS:I`LL POST A FOLLOW UP ABOUT THE NAHB`S REPLY TO THOSE FIGURES.

-- CORDWOODGUY (cordwoodguy@n2teaching.com), October 13, 2001.

JOJ...NAHB SAYS THEY ARE BANG ON!

CORDWOODGUY

-- CORDWOODGUY (cordwoodguy@n2 teaching.com), October 18, 2001.