House is in west michigan, 2004 built story and a half, 32x40 with unfinished basement, main level height is 20ft for 3/4 of the floor area. R38 attic, 2x6 exterior walls with batts I assume. 350sqft of glass, Batts in the rims haven't done a lot of work yet seeing what my baseline is. Ambient temp was 30f all weekend and tstat set point was 69f for 48hrs, this resulted in a repeatable 20225 BTU per hr.

Well you could go and punch in your numbers into this calculator and see how it stacks up. The monster variable in all this however will be your air infiltration, and without a blower door test it is only a guess. However, if you are pretty confident in the overall R/U values you use, and with stable inside and outside temps and knowing how much energy you are putting in, if the wall/floor/ceiling losses are accurate, the rest must be air infiltration... Since you can adjust it in the calculator, you can tweak that value to get the heat loss to match the heat input...

http://www.borstengineeringconstruction.com/Heat_Loss_Analysis_Calculator.html

Good Luck.

Posted By ronmar on 21 Nov 2016 03:45 PM
Well you could go and punch in your numbers into this calculator and see how it stacks up. The monster variable in all this however will be your air infiltration, and without a blower door test it is only a guess. However, if you are pretty confident in the overall R/U values you use, and with stable inside and outside temps and knowing how much energy you are putting in, if the wall/floor/ceiling losses are accurate, the rest must be air infiltration... Since you can adjust it in the calculator, you can tweak that value to get the heat loss to match the heat input...

http://www.borstengineeringconstruction.com/Heat_Loss_Analysis_Calculator.html

Good Luck.

If i use "basement" as floor type and .5 ACH the results are VERY close... it gets muddy when I try to understand how bad the unconditioned unfinished basement in hurting me.

What is your basement temp, and do you put any heat down there? How much floor insulation do you have? If the basement is all below grade, it probably isn't hurting you that much as I am sure your earth temps are well above the winter outside air temps, and the basement acts as a buffer between those temps and the main floor room temp...

Posted By ronmar on 21 Nov 2016 04:42 PM
What is your basement temp, and do you put any heat down there? How much floor insulation do you have? If the basement is all below grade, it probably isn't hurting you that much as I am sure your earth temps are well above the winter outside air temps, and the basement acts as a buffer between those temps and the main floor room temp...

Basement stays 62-63f, ducting runs down there but no venting occurs, there is no insulation between the basement and first floor, about 25% of the basement is above grade but has drywall/insulation in those areas. Also I have a 4" fresh air pipe with no damper which was required by code but I'm told since my furnace is direct combustion with intake/exhaust outside and the water heater is power vent I could safely block/remove it... I wonder how much it hurts anyway?

Posted By ls3c6 on 21 Nov 2016 06:06 PM Also I have a 4" fresh air pipe with no damper which was required by code but I'm told since my furnace is direct combustion with intake/exhaust outside and the water heater is power vent I could safely block/remove it... I wonder how much it hurts anyway?

Well it's effect will be determined by those forces in your house creating a pressure difference to cause air to be drawn into or forced out of the house thru that 4" opening. Stack effect caused by heated air escaping thru the ceiling/roof air leaks could keep a steady flow of air thru this duct. An imbalance caused by your air handler could cause air to be drawn in. Leaking ductwork could also cause positive pressure in the basement and air to flow outward. Does it flow more air at any particular time? Hanging a small ribbon in the duct opening might help you gauge relative flow strength and direction... As I am sure you discovered playing with the calculator, air exchange can pretty quickly dominate the heat use equation...

Posted By ronmar on 22 Nov 2016 09:43 AM

Posted By ls3c6 on 21 Nov 2016 06:06 PM Also I have a 4" fresh air pipe with no damper which was required by code but I'm told since my furnace is direct combustion with intake/exhaust outside and the water heater is power vent I could safely block/remove it... I wonder how much it hurts anyway?

Well it's effect will be determined by those forces in your house creating a pressure difference to cause air to be drawn into or forced out of the house thru that 4" opening. Stack effect caused by heated air escaping thru the ceiling/roof air leaks could keep a steady flow of air thru this duct. An imbalance caused by your air handler could cause air to be drawn in. Leaking ductwork could also cause positive pressure in the basement and air to flow outward. Does it flow more air at any particular time? Hanging a small ribbon in the duct opening might help you gauge relative flow strength and direction... As I am sure you discovered playing with the calculator, air exchange can pretty quickly dominate the heat use equation...

it flows a small amount regardless, i've blocked it for now.

The only real downside I could see with that if there is not a safety concern with your fueled appliances, is the loss of that steady airflow might effect the humidity down there in a bad way... A temp and humidity sensor might be a good idea for the basement just to make sure you are not creating a headache for yourself further down the road.

Good Luck.