seasonal cottage heat
 

Some friends just purchased a 40 x 26 ft seasonal camp. Built on piers and no insulation or heat other than a fireplace. They are looking to extend the seasonal usage a bit. April to Dec maybe? Exploring options to insulate floor and feel I have a good handle on that but what do folks that have a similar situation feel is best simple cost effective heat system. Floor plan is pretty open so I was thinking a couple of wall mounted propane blower units. Something like the mini split I have in my house but for heat only. Anything else they should be thinking about?There would be a total shutdown for the real cold months.

Insulate really well and go with the mini split. I would do spray foam at least under the floor. If you just have dirt under the cabin and you use fiberglass under the floor it will capture the moisture and get full of mildew, mold, and critters.
Ideally you would foam the whole place but that's very expensive.
I have a full crawl space under my house with a full cement floor, about 3 1/2 ft high. The only thing down there is my boiler.
When I bought the place it had fiberglass insulation in the floor that was wet and moldy. I took that all down and had all the walls spray foamed, best money I ever spent!
If the house is on posts then you just do the floor.

How much use?
 

Extending the season is always a good thought when you get a new place. The follow-on question is how many more days? If it is only an occasional "nice" weekend, maybe you don't want to spend too much. I'm no expert, but since heat loss goes up, I'd think you want to insulate the ceiling first. (I'm doing some upgrades on a 1910 building and that's the advice I'm getting.) Improving the efficiency of the fireplace might be relatively inexpensive with an insert and some blowers.
We have a similar size, un-insulated camp. Don't use it much after Columbus Day as we have to store the boat. We do have a couple of 220V 4000 watt electric space heaters with fans that we use on cold mornings. Our ceilings are all open rafters so no easy place to put attic insulation. I guess we could install 6" rigid foam and then cover with finish ceiling of some sort. Loses the camp image then.

We have an island camp on piers with a fireplace. For heat we have a Mitsubishi mini split and a small wood stove inside the fireplace. There is a flex stainless steel chimney liner for the stove and a sealed plate on top to prevent heat loss.

The mini split provides most of the spring and fall heat as well as summer A/C. The thermostat can be controlled via internet so we can turn on heat or A/C in advance. The wood stove helps in warm-up from a cold start.

heat options
 

Depending on how many days you need to heat, and difficulty of transporting propane, consider electric baseboard heaters. Our place on the island has electric in the bedrooms and bathrooms, and a Rennai propane heater in the main room. Electric helps get it warm faster, then the Rennai is good at maintaining.

I'd echo the insulation point. We have 4" foam panels in the roof, with only 1" panels in the wall. One thing we haven't done yet is foam insulate the floor, which will make a big difference. I'm still figuring out the best option for that. I think it will be closed cell foam, but dealing with island transport, that may make it more expensive.

We do fine with a woodstove and one medium sized Rinnai wall unit. Roof and walls are fully insulated, the floor is not. Once it's warm we turn the Rinnai off, no need to insulate the floor for us but we're out by mid October

A wood stove insert for the fireplace makes a huge difference. It's the best thing we did, other than the cabin its self. It has a blower so it heats the place up nicely.

we normally shut down first week of November because of water pipes. Ours is on piers but the prior owners had enclosed it with a block wall. 3/4 of the crawl space is still dirt.

Great advice. Thanks to all. The crawl space is pretty tight in some spots and my spray foam guy says he may not be able to get to all the areas. Place will need a new roof shortly so beginning to wonder if the $5000 or more it would cost to spray foam under floor would be better spent on a new insulated roof. A chilly floor can be addressed with a nice pair of slippers.
For heat I am leaning towards a rannai for the majority open area with a few small electrics for individual bedrooms

If it is on the main land, not an island, and propane can be delivered by propane company, a Rinnai propane, direct vent, space heater is very reliable and very fast heat. Their direct vent models are a totally different animal than their complete combustion models which do not vent the combusted propane to the outside. Yes - direct vent ...... and great big NO to the complete combustion models. Regardless what anybody says ..... I can still smell the propane with the complete combustion which is basically impossible to do .... is like having a wood stove without a chimney to exhaust the smoke.

A Q-tank is a 125-gal, fat vertical tank that occupies about a three foot circle of the yard, weighs 400-lbs when full, and it works good with a Rinnai. It has enough pressure with a 3/8" line to power it up, along with 110v to power the starter, blower, and control.

Suggest you talk to Dead River, Rymes, or Eastern about a Rinnai installation and tank plus propane supply for one source provider.

Another very important item for a semi-seasonal cottage is a heated mattress pad that goes on top of the mattress, and under the sheets. Is 110v, about $50, from Ebay ...... made by Biddeford or Sunbeam. A heated mattress pad makes a big difference! Makes it possible to turn the room heat way down to very low while sleeping, and not be bothered too much by a cold floor.

It gives you a big psychological boost knowing you always have a good warm sleep!

For a semi-seasonal cottage, a heated mattress pad is like the best 50-bucks you can spend!

WinterH,
A simple way to combine a roof replacement with insulation is to use overlap metal roofing and 1.5 inch foam. Install 2x4s laid flat and 2' apart as your roof purlins and then drop 1.5" sheets of foam between the purlins. If your rafters are already fairly strong you might even be able to place the purlins 4' apart, still have a solid roof, and save some on the high cost of lumber. Best part is that even if you don't have a lot of mechanical skills you can probably undertake this relatively simple project. An inch and a half of foam, especially if it is reflective faced, lining your roof will make a huge difference both summer and winter ...and might this qualify for a energy improvement tax credit? I don't know but it is certainly worth asking

You'll have a very tough and/or expensive time keeping the place warm without an insulated floor. One way or another, you really need to do the whole thing