Heat Load for greenhouses.

Wayco Wayne_2

How do you do a heat load for a greenhouse? there's no walls, only glass. A little help please.

Mark Eatherton

R what?

Single pane would be R 1 to 2, double pane could be R 3 to 5 (with gas) and triple pane could be R 5 to R 7 (also with gas).



Infiltration could be the killer..



A over R times delta T = conductive losses.



Plus infiltration at .018 btu/cu ft/minute times the air changes per hour.



ME

meplumber

Greenhouses are a little different.

While Mark's method is the more scientific approach, the greenhouse people usually have a heating package geared for the horticultural intent.



They are usually done for Seasonal, Local, Tropical, etc... That drives the design temp and humidity. Tropical greenhouses are normally designed for 84 F year around indoor temp. Seasonals are 72 F shoulder and 60 F winter indoor temp.



Greenhouses are the only buildings that I do a radiation only survey on for boiler replacements and even new installations. Because the greenhouse folks always spec the radiation amounts.



Good Luck.

Wayco Wayne_2

Thanks

for the input. There are two old rusty peerless boilers rated at 845,000 IBR. There is a primary loop out to the greenhouses with pairs of close tees and a circulator every place they want a zone. I'm thinking of taking out one boiler and putting 2 or 3 mod cons in its place. (for economic reasons.) I'd have all boilers teed into the primary loop and a boiler control staging the boilers in and out. I'd use the old peerless cast iron beatie as the last dollop of heat in the colder weather. I will do a heat load but I agree it would only be a SWAG

Bob Gagnon plumbing and heating

Delivering Heat

What are you using to deliver heat in the greenhouse?



Thanks, Bob Gagnon