hydronic retrofit for old farmhouse

JAtch

We need to make some decisions soon about the heating system in a single family dwelling, an 1840 farmhouse, currently set up with two rental units. This house is next door to our primary residence (1850 farmhouse), and whenever we invest in systems for either house, we focus on choosing an alternative that makes the most sense over the long term. From that perspective, energy efficiency is a basic tenet for our house decisions, and we believe one that always makes good investment sense in our central Vermont heating climate.

We have a Vermont state energy incentive to replace the electric domestic hot water (dhw) heater and we want to use another state incentive for solar hot water, and possibly photo-voltaic (pv). (The house has ideal placement for solar panels.) We believe that we want to change the whole house over to hydronic heating, with separate zones for each of the rental units, possibly phasing this in, with a change to only the dhw system now.

We need to make decisions in the next month to take advantage of state incentives, which has brought me to the Wall over the past few weeks, to two heating contractors (no proposals yet...), and to multiple books. (Thanks to Dan for "Pumping Away"...) The more I read and understand the options, the more important it seems to be explicit with any contractor about about what we want. We'd like to provide some basic house facts and hope that you all may have some thoughts/suggestions, general or specific, to help us with these decisions.

General info
The house is a 1.5 story square farmhouse, (mainhouse), and an attached apartment, (the 'el'), which is the expansion of a mud room with an 2nd floor bedroom and bathroom. The latter has been carved out from a bedroom in main house and the units share a north wall. The house has dense packed cellulose insulation throughout; this month a siding/insulation job upgraded the cellulose and and added a layer of .75 high performance foamboard on the sheathing, capped by the vinyl siding.

mainhouse

sq.ft- down= 590; up= 415; total= 1005

rooms- up= 2br, .5br; down= lr/dr(open area),br,k,bath

occupants- 3-5

basement- full, unfinished, stone and cement wall, dirt floor with plastic on top

heatSource- primary is large wood stove oil furnace, circa 1980

wood floors-old wood, with wood (not plywood) subfloor. carpet on old subfloor in 1 br upstairs which has only upstairs heating duct up


el

sq.ft- down= 352; up= 235; total= 587

rooms- up= br, bath; down= k/lr/dr(open area)

occupants- 1-2

basement- crawlspace, reasonably insulated for half, cement crawspace well insulated for other half-(plastic over dirt for both)

heatSource- propane (lp) gas vertical wall furnace (new 1989)
wood floors-old wood throughout with plywood subfloor

hot water- electric 65 gal, circa 1990, with about 5 years full use, serving both units. (The house has a single electric meter.) Temperature is set at 120F; last year's dhw utilization was about 50,000 gallons.


Other info/thoughts

The wood stove is centrally located on the mainhouse 1st floor and can effectively heat all that space; heat goes upstairs via a ceiling vent and the wide stairwell. Only one of the upstairs mainhouse rooms has a heating duct running to it, providing a good chimney chase for future piping. As the hearth is a central feature of the mainhouse downstairs, we believe that there will always some form of wood heat in the house, although that might become a pellet stove in the future.

Any new heating devices should not be lp gas; oil probably, but we have thought about geothermal. Lp gas will still be in the house for dryer and cooking, and we'd consider using it for a dhw instantaneous heater.

We do want to put in a single heating system for the house because we believe overall it's most efficient and because a priority is maintaining the single family nature of the house.

The mainhouse downstairs has gorgeous old woodwork in the main part, so baseboard is not appropriate there. The el also has extensive woodwork throughout so we are wary of baseboard there also. Any alternative radiant devices should be as unobtrusive as possible.

We want to fully utilize the solar hot water, both for dhw and possibly to supplement hydronic heating. Given that, my reading suggests to me focusing on some type of low temperature system.

The best alternatives seem to be hydro-air, alternative radiant devices or radiant floor. The latter is not a good alternative for the ground floor of the el because of tar paper and the crawl space restrictions. We have some questions about the effectiveness of radiant floors on the wood floors in the mainhouse but perhaps that would make sense in conjunction with a wood heater on the hearth. We realize also that our desire for a low temperature systems may conflict with our desire for unobtrusive alternative radiant heaters.

A solar installer suggested a solar pre-heating tank with an instantaneous dhw heater drawing from it. We wonder whether a small boiler with an indirect dual exchanger tank would work better; has anyone had experience with Viessmann tanks which seem explicitly designed for solar? If we were to install a new boiler, we would want a condensing modulating device. (We know Viessmann offers such alternatives but also know their cost may be prohibitive.)

We'll want to be able measure in some way the heating resources going to each unit. (We currently have flow meters on the hot water pipes that permit fairly accurate estimates of each unit's dhw utilization.) Such a device need not perfectly measure utilization but should provide some means of allocating the single heating system resource costs to the two units.

Given all our concerns, we have questioned whether it might make sense to buy a hydronic design and then just use those specs to find a reliable conractor with the lowest bid.

This can be phased in over a number of years. Having just upgraded the insulation with the siding job, we wonder if perhaps it makes sense to wait on any heating change until there is some feedback from next winter's heating experiences. (Vermonters also have long lived by the adage "If it ain't broke, don't fix it...") If that were case, we want to do something with dhw now that will be an initial step in a longer term move to a hydronic system.

In advance thanks for any thoughts, suggestions and ideas...

joe_17

come on

you mean that house was built in 1850 and its still standing.i dont believe you.wasnt that before custards last stand!

Lauri

First, best of luck. You have a lot of choices.

I'm a homeowner with a pretty similar situation (central VT, 1860's farmhouse). We just finished having radiant installed under entire first floor plus an area above our garage. Though it's now relatively mild outside, the system feels wonderful (after living with just wood stoves).

The pex runs under our pine floors downstairs and in mortar upstairs. Response time is very slow; it took about 24 hours to get it up to temperature initially. We have a Polaris propane boiler (96% eff., quiet) and a 40-gal indirect storage tank for domestic hot water.

I'm just looking into the solar hot water incentive too, and it looks like I would need another large storage tank, in addition to my 40-gal tank. Logic: The 40-gal tank is too small to handle summer-time solar heat, and a big tank would be wasteful to keep heated during the many sunless winter days when the Polaris would have to do more work.

Obviously you have lots of questions I can't answer, but if you'd like to come check out our system, let me know. You could probably give me some insight into the solar application. Email: lauri@vtexplor.org. (I'm in Middlesex.)

Matt Undy

hybrid system

perhaps yu might consider using a boiler to make DHW and radiant/radiation where there is space and using high velocity forced air and fan coils where there isn't room for adequate radiation? I'm just a h/o and engineer and in forced air country, so i only know what i've read about hot water and steam systems, in fact i've only see a handful of residnetial steam or hot water systems.(of course it seems to me that zoning with a few condensing furnaces tucked here and there is less expaensive and nearly as efficient as doing it with an elaborate hot water and control system.

Matt

Matt

JAtch

Thanks for your thoughts. Lauri, we are in Waterbury so it will make sense to share our experiences. I will make use of your email soon. Mat, we wouldn't necessarily be averse to an oil furnace solution but we've not seen any oil units as compact as lpgas wall furnaces; that is a bit of a problem because of limited space. Would separate furnaces need their own tanks? If multiple units can be fed off from the same tank, is there a way to measure the oil going to each? thanks again for your time and thoughts...

Matt Undy

Opps, I forgot aobut the oil aspect. I'm just a HO and EE so i'll have to defer the specifics of the oil to the pros. I'm not sure if there are condesing oil furnaces that would fit in a confined space well. I'd imagine off the same tank is feasible and somone out there makes a meter sutible for oil, but that is pure conjecture. Another consideration may be that the added expense of oil, hydronic, and fitting into the available space may be so much more expensive that the payback isn't worth it when equipment life, and financing of the added expense are considered. Also, there is a thread here somewhere aobut issues with renters and non-payment of fuel bills.

It looks liek the situation is complex enough that you need to find somone that knows hydronic, fored air, hybrid hydronic sytems makign wram air, and both oil and LPG to look at what spaces are avialable and giv eyou soem ideas of costs for each type. Its liekely that some sytems will be a lot easier to install in your particular spaces than others.

Matt