Vacation house heating opinions

Dan_8

Sorry for the long post. It always seems to be better to put in more details than less but then I end up writing a book...

My family has a vacation house on Cape Cod. It’s about 100’ off the water in Dennisport if any of you know the area. It belonged to my grandparents who left it in trust to my mom and her brothers and sisters. Because it's a typical committee trying to design a camel lots of things either don't get done or get done in a truly haphazard way and I think that the heat is in need of attention down there.

It currently has what I think is a dangerous, inefficient and untrustworthy heating system. The boiler is a 40 year old Weil-McLain which has done a great job but it is certainly showing its age. It's oil fired, I think that the burner is about 15 years old. It puts the heat into the house using fin-tube baseboard which pretty much wraps the perimeter on both the first and second floors. Hot water comes from a coil so the boiler runs hot all the time. The dangerous part (other than the fact that you can see flame through every door gasket on the thing) is that the boiler flue is joined to the fireplace flue about four feet above the fireplace damper.

So... I'm assuming that I have everybody on board for this thing needing replacement just for the flue alone? Carbon monoxide issues must be getting everybody's typing fingers itchy. Besides the fact that I love my family and don't want any of them to be hurt by a sleeping seagull blocking the flue we rent the place during the summer and I imagine that the potential liability is probably enough to break us all.

I love the house dearly so I have a hard time bad mouthing it but it's really not built all that well and certainly not insulated very well either. I'm having a hard time nailing down a design temp for that area but I'm guessing in the -5F range but rarely with long spells of that and far more often a raw, blustery 30F. My rough numbers on the place show something on the order of 130MBTU at -5 and about 67MBTU at 30. When the wind is blowing the infiltration has to be off the charts though. The house is really only occupied on weekends during the winter so the inside temp can come down to 55-60 which changes the heat loss substantially. Given a 55 inside temp (which is about where we set the t-stat when it's unoccupied) I'm showing 108MBTU and 46MBTU at -5 and 30F respectively.

Because of the design of the house and the chimney, getting another vertical flue up there would be either incredibly expensive or really ugly so I think that a side venter is the way to go. I generally lean toward oil heat for cost reasons but here I think that there are two excellent reasons to go with gas. First, side venting gas exhaust will be much less likely to be noticed (although I do understand side vented oil can be okay) and this house is used on all four sides and has lots of windows. Second, if we get on the gas pipeline we don't have to worry about running out of oil while nobody is there to check on the house.

There is about 180 feet of baseboard in the house (I'm approximating but pretty sure that I'm close). That means that when it's occupied I've got to pump about 700 BTU/ft at -5 but only about 375 at 30. When it's unoccupied I'm looking at 600 BTU/ft at -5 and about 250 at 30. I don't have any charts on this particular baseboard (it's about the same vintage as the boiler) but if it's similar to current stuff I should be well into the condensing range for a gas boiler at an outside temp of 30 and an inside temp of 55 (and probably in that range quite a bit more than that).

So, I think that we'd be pretty darn happy with a nice little modulating gas boiler like the Munchkin or Weil Ultra. I like constant circ and reset but we’d certainly need to have a controller that could understand how to come off of a deep setback reasonably speedily. Add in a good sized indirect (when the house is loaded up the showers can be nearly continuous) and we'd be super happy for years to come. My feeling is that the *huge* efficiency jump from our current setup would more than offset the extra expense of gas and that we'd see a net savings, especially from summertime usage with the massive boiler that we have staying warm all the time.

Anyway, I'd really like some feedback if anybody has it. I've been thinking about this one a fair bit for quite a while now but you're the folks in the know. Thanks for any help.