Heating and cooling system suggestions
Gonediesel
| Posted in Energy, Heating & Insulation on
I am looking for some basic starting advice on furnace replacement. I am in a pretty rural area and getting pros to discuss things are kind of tough. So I have a furnace that is on its way out and now is the time to plan for a new system. My house has infloor hydronic heating but no boiler system currently. It is currently heated only with a propane furnace. So the question is what would be the pros and cons to have two separate heat sources, boiler for infloor and furnace for forced air heating vs having a single unit do both?
Replies
Twice the cost for two systems.
You could go with a boiler for the radiant floor, and put a hydronic heating coil on an AC air handler (assuming you want AC. even if not, all you need is a fan) to utilize the ductwork for forced air heating.
But: Is the house decently insulated, and in a mild to moderate winter climate? Then maybe the radiant floor is all you need anyway?
Going one step further, a single source can be used to provide hot water, radiant and forced air. There are a number of tankless 'combi boiler' vendors with systems set up specifically for this application. A tank type water heater can also be set up to provide heat for the radiant floor and air handler, by using a heat exchanger to separate the heating side from the potable water.
The main drawback to a combined system is the effects of a failure. If there is not another source of heat, i.e. fireplace, it could be an issue. If that is the case, using combination DHW and radiant heat, and a separate furnace for the forced air may be better. The furnace should be sized taking into account the heat provided by the radiant floor.
You might want to look at heat pumps, considering the cost of propane.
If you are up for it, and considering long term costs, you might even look at a ground source heat pump. you can add a desuperheater and get hot water out of the unit as well as hot or cold air.
The hard part is a ground loop. having a pond would be ideal, or you can dig either wells or a long trench to lay the tubing in.
This would end up complicated, and if you rely on a local technician for service, you would need to have one up for the tasks.
a first step would be to understand the heating and cooling loads your house presents.
After doing a little reading, using a tankless boiler for both infloor and hydronic forced air is what I guess I am looking for. Seems pretty simple.
We have pretty high priced electricity in our area and propane has been quite a bit cheaper. Our neighbor works for the electric company and has given me a breakdown in the past on what point it would be cheaper to use electric to heat via the different methods (geo, heat pump, etc) and propane would have to more than double. This was about 6 years ago and not sure how much more effiecient the alternative heating methods have gotten. I have a friend who has geothermal and cooling has been the biggest savings and he thinks he could heat with propane cheaper. Not sure myself. I have called in to get a full evaluation. The company I called does geo so will talk about those options. Regarding failures, I am the guy who has a spare for the spare. We have several large electric heaters that have come handy when propane ran up over $5 gallon several years ago. We are in the woods and when I have this work done I will have it plumbed for a wood boiler system. I had to run a new sump line out and it required a bit of excavation by hand. Not wanting to ever do that again I prepped it for future projects.
I meant to add we are in WI. -20 right now. I personally think that the furnace and or ducting wasn't planned correctly or it was planned to have infloor running in combination. I am hoping once the infloor is running it levels out the house. I would like to get a variable furnace blower and possibly also have it automated for two zones. Looking at the ducting routing it seems like it would be an easy task. The house was built in 2007 and in my opinion is insulated subpar. The attic insulation has settled quite a bit and I have spent some time up there disturbing it running electrical for additional lights in the kitchen, new network lines, coax, and placing a large HD OTA antenna in the attic. We have purchased the insulation and had planned to blow it as soon as I was done messing around up there. Was hoping to get it done in the fall but now waiting for a weekend in the next month or so. Looking at the prices of materials right now I am freaking glad I bought the 30+ bales of insulation when I did.
Do you have a heat loss calculation ( Manual J) for what the house will be after you finish the updates? Will give you a better idea of the size of heating system needed.
A heating contractor should do that when specifying the replacement furnace , or you can use an online calculator if you are DIY: https://www.loadcalc.net/
Also, the output capacity of the radiant floor is needed. Do you have the layout and construction details? Slab or floor joist? Heating tube size & spacing?