No lectures please, I didn’t design this. New 1000 sq ft PanAbode cedar log wall 3 season cottage/fishing camp in Western Quebec on cement piers w/ cathedral ceiling, windows/sliding glass doors covering a little over 1/3 of wall area, 18 - 21x45” skylights. . . . . . . .anybody vomiting yet?? This building is for the managers (my wife and I at the moment) who will be in house 24/7 from late April to end of October. (The owner’s building is identical design but 1700 sq ft). We are not interested in AC, heat is required from opening to +/- June 1 and again from late September to Nov1. I will be installing “sandwich” HR under hardwood. I’m presently doing a “heat loss analysis” with the Borst calculator and have a few questions. 1) for ODB temperature I used the mean average for October, 47F, which is close to the same as the springtime mean.2) Skylights, which have the same U value as the windows, I included with window sq footage and deleted that amount from ceiling. 3) Fireplace ?? Corrections please, and thank you very much.

1) This is typically the 99% dry bulb temperature for the local climate. See ACCA Outdoor Design Conditions.

2) That’s correct, but there will also be a solar heating component as well...perhaps beneficial in Winter, but not in Summer...

3) An open hearth fireplace is an inefficient, extremely polluting way to burn wood that has no place in any house these days. Fireplaces significantly worsen the infiltration rate and the infiltration rate is the the most challenging heat loss component to estimate. Perhaps consider decommissioning and removing the fireplace. 1.0 ACH might be representative of an older, leaking building. 0.5 ACH might be representative of new construction.

Thank you sailawayrb.

I agree on the fireplace but it’s not my house and like the couple driving the 40 foot motor home and towing an SUV, it’s not my place to tell them what not to do. Having said that, I grew up in the 50s with wood heat, am paying the price and would never have it in MY house.

Question: I realize I may be premature in that doing a tubing layout to calculate head is probably necessary to accurately specify circulator requirements BUT on a 1000 sq ft house wth a total heat loss calculation of 14,500 BTU/hrs, 5 loops, 3 zones, sandwich under .6” eng. hardwood, anyone care to do an educated estimate on the circulator electrical draw?

You can use a smart ECM circulator that will likely use less than 10 watts. A more conventional PSC circulator might require four times more watts. What heat source are you planning to use for your 14,500 BTU/hrs (4,250 watts) 99% design heating load?

I had come across the Bell & Gossett ecocirc e3 Circulating Pumps and was going to ask for user opinions on their pumps. The El Sid DC pumps look interesting as well. More info on the solar side of this board I suppose. Propane is my heat source.

If you're only heating between late April and early November there's no need to design to the 99th percentile temperature bin for the year, since those temperatures literally NEVER happening during the time frame it's being heated, only during the winter months.

It might be worth looking up the coldest temperatures for the months of April and October over the past five in that location and use whichever is colder as the design temperature. Using the mean temperature for October would undersize it by quite a bit, but using the record cold (or the coldest temp for the month in the past 25 years) would have you covered. It's probably going to be more than 10C warmer than the 99% outside design temperature, which eases the requirements of the heating system by quite a bit, but not so much that it would leave you cold during a rare April Polar Vortex weather pattern.

For instance, the 99% outside design temp for Val d'Or is -22F, but this year the coldest temperature for April 2017 was +17F, and the coldest temperature for October 2017 was +25F:

https://www.wunderground.com/history/airport/CYVO/2017/4/20/MonthlyCalendar.html

https://www.wunderground.com/history/airport/CYVO/2017/10/20/MonthlyCalendar.html

Designing for the heat load +17F instead of -22F is almost a factor of TWO, and it's 39F (22C) warmer than the 99% outside design temp.

Using heated floors is quite an extravagance for only 2-4 months of use out of the year. Even though you're not interested in the air conditioning, a Fujitsu -9RLS3 can probably cover the heating load at a lower installed cost and lower operating cost than a propane boiler (or water heater). And unlike the propane fired hydronic solution, it doesn't have to be protected from freezing during the winter. At +17F the 9RLS3 can deliver 22,000 BTU/hr at it's maximum speed, which is almost certainly more than the heat load at +17F.

I suspect you will be challenged to find a small enough propane heat source that won't be significantly over-sized for your heat load no matter what you use for your design outdoor temperature. However, I get the impression you are more concerned about comfort than giving up some efficiency.

Thanks Dana1. I used 30F for my outside design as that is the lower end of when we are in-house. You’re right, radiant floor heat is an extravagance, but then so is a million dollar fishing camp. Owner doesn’t want to compromise by having white plastic radiators in front of the gorgeous western red cedar walls. Regarding mini splits, at 7 amps for the smallest 115v 9k Fujitsu that creates just too much draw for our solar/battery system. Having said that, I realize that’s not continuous so I would be interested to know what the 24 hour draw would be at my ODT and heat loss calc. Simple math for you, right?

Sailawayrb, What are your thoughts on adding the previously mentioned 1700 sq ft main cottage to the equation? There’s a shop between the two cottages, 50’ to one, 75’ to the other. Is it possible to run both off one boiler located in the shop?

That would certainly be possible. You would just have to properly insulate and size the distribution plumbing. Dana's mini split solution has merit. Can you increase your solar power capacity?

I’ll take both options to the owner when I meet with him in a couple weeks, and in the meantime thank you both for your input.

Posted By RBF on 06 Apr 2018 09:08 PM
Thanks Dana1. I used 30F for my outside design as that is the lower end of when we are in-house. You’re right, radiant floor heat is an extravagance, but then so is a million dollar fishing camp. Owner doesn’t want to compromise by having white plastic radiators in front of the gorgeous western red cedar walls. Regarding mini splits, at 7 amps for the smallest 115v 9k Fujitsu that creates just too much draw for our solar/battery system. Having said that, I realize that’s not continuous so I would be interested to know what the 24 hour draw would be at my ODT and heat loss calc. Simple math for you, right?

A mini-ducted minisplit with high throw registers can get you there without the wall-coil blobs. Putting them at the ceiling or partition walls would be best, but floors are possible.

http://www.greenbuildingadvisor.com/sites/default/files/2015-11-04%2010.35.14.jpg

http://www.greenbuildingadvisor.com/sites/default/files/2015-11-04%2010.35.28.jpg http://www.greenbuildingadvisor.com/community/forum/mechanicals/93846/mitsubishi-minisplits-horizontally-ducted

The fact that most DECENT mini-splits are all ~240VAC and minimum ampacity may be show-stoppers if the PV has already been specified. It general for off-grid it's best to go with something that uses no power, or very low power. Even a hydronic pump and atmospheric drafters propane water heater solution will use quite a bit of power. Hydronic floors will use more power than say, panel radiators due to the higher pumping head and higher duty cycle. Heating solutions that requires air handlers and compressors (such as mini-splits) will use even more power.