Heat Loss Calc Input Help

You can use 250 for the altitude. Outside temp would be between 10 and 15 degrees depending on your exact location but this will get you close. Use 180 for the system temp.

Hello gorsuchmill

I'm not too far from you; I live in Carroll county. I've been exploring the possibility of installing a wood boiler so I also used the Slant Finn calculator. I've talked to a couple of HVAC contractors about installing an additional heat-pump for my 2nd floor and my heat-loss calcs seem to match pretty close to what they've come up with. I used 0 degrees for the outside temp, it doesn't get that cold here too often but it can and does. My altitude, according to GPS, is 730 feet but changing the altitude to 10 feet didn't change my btu rating at all so I don't think this value really matters much in our case. I used 180 for System Design temp.

I use this. Overtime these numbers seem to have changed. I read some older books that have differing numbers. Eitherway plus or minus about 5 degrees is fine. Also slant fin seems to be very conservative in its calcs. Just thought I would mention it.
http://www.engineeringtoolbox.com/us-outdoor-design-temperature-humidity-d_296.html
Here is my slant fin
http://www.innovativesolutions.cc/boiler/images/heatloss.jpg