Heat loss calc ?

Mike T., Swampeast MO

Have been thinking deeply about this problem.

Is there a basement or substantially below-grade space? If so, how did you compute the loss for such?

Closets without radiation and perhaps outside walls in addition to ceiling losses? If so, did you consider them as "part" of the associated room without using "cold walls"?

Any compensation for transmission loss?

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When I consider what I INTENTIONALLY left out of my heat loss--small radiant floor baths and ANY loss in a completely uninsulated, triple wythe brick foundation that averages 50% above grade with 100% above grade to the North--I'm REALLY wondering about your amazing difference between calculated loss and actual consumption!!!

Once completed, I FULLY expect my actual loss to be around 70% of calculated. When I again consider what I left out and did my best to "compensate for", 50% actual-to-predicted seems more and more reasonable!!!

Garret

I stumbled on this the other day... not sure if it's what you're looking for.

http://www.burnham.com/pdfs/htghelper.pdf

Page 47... There's a chart giving the heat emissions for cast-iron rads at design temps from 110 to 215 degrees.

A quick transcription is attached...

Mike T., Swampeast MO

Steve:

Am working on a completely new heat loss calc for my house (HVAC-Calc). Am including everything I intentionally left out before (basement, large closets with exposure, RFH baths, etc.)

Am curious to see what happens as I'll be ADDING load, not subtracting...

S Ebels

Should be interesting

Out of curiosity Mike, what was the original load for your house and what design temp and infiltration factor did you use?

Mike T., Swampeast MO

Oh is it EVER interesting...

Infiltration factor "average". Have checked--nobody in town offers a blower door to verify. Perhaps I'm too high. 1903 home. Balloon framed. Solid shiplap sheathing has shrunk to the point that the shiplaps no longer shiplap--e.g. about 3/8" visible gap. Tar paper and fiber-cement siding. Original windows--completely restored with spring bronze weatherstripping and aluminum storms. 3½" fiberglass in the walls.

Should I call this "best"??? Perhaps input a value somewhere in between?

Original loss calculation: 80 MBH; 70°F in; 8°F out

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JUST finished the new loss calculation (Found some errors today--notably omitted floors resulted in zero infiltration for basement and improper total for ground & 2nd floor. Also somehow forgot that the 12'x12' 3-floor addition I made to complete the full rectangular basement footprint used ICF and insulated studwall foundation!).

114 MBH; 70°F in; 8°F out!!!

Were I to classify this loss calculation, I would say "done by a thorough, competent technician with intimate knowledge of the construction".

ONLY caveat to that statement is my treatment of the basement. Solid brick. Completely below grade at the front--completely above grade at the back (north). Even slope along the sides. MANY doors and windows in the basement.

I considered the basement a "separate house" so I could use different indoor design conditions.

Computed loss ONLY for that amount of foundation above grade, doors and windows. DID NOT include below-grade foundation. Included floor as "over condition space"--NO LOSS, but required to compute infiltration. Used 45°F for the basement indoor temp, AT LEAST 7° lower than the lowest temp I've EVER recorded via the datalogger--including sustained outdoor temps below design.

12 MBH loss for the basement. Will verify, but believe that's pretty damned close to a reasonable output from the intentionally uninsulated piping at the north end of the basement plus the rest of the nicely insulated (main and branches) piping.

For main house, used "unheated basement" below the ground floor.

Any suggestions on how I could improve? If I'm REALLY trying to compute loss it's hard to ignore a basement that averages 50% above grade and has 2 garage doors with windows, 4 glass doors, 1 wood door and 6 windows!

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To the utmost of my abilities to ascertain, my ACTUAL loss while maintaining temperature at design conditions AT NIGHT WITH MODERATE WIND is 64 MBH. This with the house in the PRESENT STATE. 2nd floor complete. Downstairs in rough drywall. No window/door casings. No window/door weatherstripping. No window weight pocket insulation.

64 MBH actual vs. 114 MBH predicted = 56%

When complete and some occupancy gains from mechanics?

BELOW 50% would not surprise me in the least!!!

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Here's the bombshell: Last year (the first with the Vitodens) the ground floor was in bare studs! The ceiling below my wonderful 20' above-grade 2nd floor balcony was completely uninsulated. The big walk-out bay window in the dining room was LOOSE!!! At 61° MINIMUM indoors and sustained below design temp weather, dear Vito still had SIGNIFICANT remaining capacity! (Search old posts and you'll find the input.) Ceiling below balcony now has 6" of meticulously fitted and sealed rigid insulation; the bay now has MANY cans of foam.