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1st home
Best way to add central AC

My husband and I are in the process of buying our first home. The 1885 approx 1500 sf 2 story Colonial house is in NW metro Boston. From an HVAC standpoint, our priority is to insulate the house (there is nothing now) and add heat to the rooms lacking it. It is not clear why the half bath and the office lack heat but I do not want to continue the practice of electric plug in heaters in the rooms.
Our next priorities are:
- to address the older heating system. The house has an ~25 year oil boiler for forced hot water heat with cast iron radiators and inline DHW.
- to add central AC. While we don't get a ton of super hot days (this year was an expection), my husband has allergies and drier cooler air is better for him.
- to switch to a gas system. It is available at the street, not brought into the house yet.
- provide an energy efficient, as possible, solution
My husband wants to keep heat and cooling systems separate and install mini-splits for AC but I don't like the look of wall mounted boxes on the walls and I think that buying a bunch of units would be more expensive first costs and long time costs than a central system. My question for the board is, do I just add a duct system for the AC and keep it separate from the heating or do I change the heat to forced hot air? If everything was forced hot air, I wouldn't be able to have radiant heat in the bathrooms which would be really nice.

Re: Best way to add central AC

Personally I would stick with the HW heat and install high velocity AC units. You would only have small ducts and ceiling outlets about the size of small recessed lights.


Re: Best way to add central AC

I would tend to agree with JLMC (as well as your husband) for several reasons.

First, I feel a forced hot water system, especially one with cast iron rads (over baseboard) is a superior type of heating system over FHA; since you already have the FHW distribution system in place with the rads, it would be nuts to rip it out for something else.

By all means, your first priority is insulating the entire house---it's a big waste of money to have all that expensive heat and AC just escaping thru the uninsulated walls---something that should have been done years ago by the previous owner.

Consult the Yellow Pages under "Insulation" & find contractors that specialize in blowing in cellulose insulation---it's done from the outside of the house by removing a piece of siding here & there, usually completed in one day; this is money well-spent; it will pay for itself with all those saved heating/cooling bills in future months & years--you need at least R19 in the exterior walls and R40 in the attic.

If the boiler itself is 25 yrs old or more consider replacing only the boiler---this could be a boiler that runs on nat gas for approx. $4k to $8k so that you would eliminate annual cleanings & other service woes connected with an oil system----make sure to have the boiler installer do a HEAT LOSS CALCULATION, since the new boiler can be smaller (and thus burn less fuel) than the old one; be sure to tell the installer that new insulation has been installed thru the entire house.

It would be a relatively easy matter to "add-on" any radiant floor heat sub-sections for the baths, office, etc., to the present HW distribution system, but get cost estimates first; there are other less costly solutions such as FHW kickspace heaters, new stainless steel designer rads, baseboard, or even small FHW rads.

You should not close your mind to mini-splits for the AC, which are effective & quiet & usually the least expensive way to install AC; at the same time also check out the UNICO high velocity AC system that JMLC mentioned; consult the Yellow Pages under "Air Conditioning" and get several estimates for each system before you decide.

Also call your local gas utility, I believe it's National Grid in Boston---they often have deals where they will install a new gas boiler at reduced rates if you agree to switch from an oil-fired boiler to a gas-fired boiler.


1st home
Re: Best way to add central AC

thanks for the advice JLMC and NashuaTech. I'll look into the small duct system option. Putting equipment in the attic is not an option because it is finished but I'm sure that there are way to have everything in the basement.
NashuaTech, I wish that we had the opportunity to take advantage of National Grid's rebates but the town has its own utility and therefore, we don't qualify for NStar's programs. The town's rebates are minor.

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