System Design

GMcD

Solar control for windows: long story short- exterior shades, deciduous trees, tinted exterior glass, low-e coatings, anything that will shade the glass (depending on orientation) so you keep out the solar gain in summer, but allow it in during the winter. Rolling exterior blinds, Euroshade adjustable louvres, etc. Keeping the shading devices on the outside works best. Using interior blinds just allows the blinds to absorb the solar load and act like radiant heating panels in the room on a sunny day.

I understand the need for humidity control in your location. If you can reduce the cooling loads to the bare minimum, you could probably get by with a dessicant type energy recovery ventilator with s vary small split system heat pump AC unit (or geo-x?) and keep the hydronic heating for zone control and winter comfort.

Mark_46

System Design

My home is currently using a gas fired 40 year old American Standard steam boiler. Needless to say, it's time for replacement as the house is not confortable and the furnace is very inefficient.

But, we also want and are prepared to take the plunge and install central A/C as well.

So, on a high level, any good starting tips for system type/design and furnace selection?

I figure forced hot air is the way to go which would avoid redundant systems. By this I mean e.g. hotwater baseboard for heat and duct work for AC. We could get both with forced air.

In this case, first floor registers would have to be in the floor (up from the basement) and the second floor in the ceilings (down from the attic). This would also require two small furnaces and A/C evaporators. correct?

Or would this configuration be totally nuts?

GMcD

First step

Define your budget and goals. Then look at options starting with the building envelope. Depending on your climate zone, taking some or all of the $$ dedicated for new added AC can be used for new windows, solar control and improvements to the envelope to avoid the need for mechanical cooling in the first place. Improvements to the insulation, infiltration/air leakage issues will also reduce heat losses, reducing the size and cost of the new replacemnt heating equipment, too. Instead of looking at it as a straight "need a new furnace, and while I'm at it, let's add AC too" job- see how much you can afford, set some goals for what you want from the project, and then look at "whole house options". You may be pleasantly surprised.

Mark_46

Yup

Geoff,

Thanks for your thoughtful reply.

Our goal is comfort. Even heat and (for me) humidity reduction. Cant stand humidity! Plus, of course, cooling capacity on the really hot days.

Your right, the house itself is an issue and agree it's part of "the system". Windows are already on our to-do list but insulation is a sticking point with me. Im not comfortable with what seems to be the only option, blown-in cellulose. Lots of holes either in the plaster or the sheething.

As to our climate, we are in Northeastern New Jersey...15-20 miles outside Manhattan. Probably avg summer temp is 80 and winter 30.

May I ask, what do you mean by solar control? I assume you mean performance windows with low-E glass?

Mark_46

Explain?

Geoff,

Great info. Very interesting. But I'm afraid you lost me.

Could you expand on "dessicant type energy recovery ventilator with s vary small split system heat pump AC unit (or geo-x?) and keep the hydronic heating for zone control and winter comfort"?

So this configuration is a heat pump (furnace) that can cool as well. Then, the dessicant ventilator would handle the humidity in lieu of a larger A/C unit, correct? Basically a small A/C unit with a separate humidity control system?

And when you say "keep the hydronic heating for zone control", hydronic meaning steam or heat pump? Are heat pumps available in forced air type?

GMcD

Caught in a jargon loop

OK, in my jargon "hydronic system" would be steam or hot water created by a fuel fired boiler. Some folks call the boiler a "furnace", too, so I am not sure what your jargon means.

A dessicant type energy recovery ventilator is usually a heat wheel type of unit- do a google search on the words dessicant energy recovery unit and see what comes back. Greenheck is a common brand name and there are others. These units are designed to de-humidify the incoming ventilation air and extract energy (cooling and heating) from the air being exhausted out of the house to pre-heat or pre-cool the incoming fresh air. This type of unit will remove some of the incoming humidity on it's own, but you'll likely need a mechanical cooling section (small split system or ground source heat pump) on the supply air (fresh air) supply to the house for the final de-humidification and cooling control.

The steam boiler you have can be replaced with another steam boiler and you can re-use the terminal heating devices (baseboards or whatever) and you can use a small air to air energy recovery unit to provide your basic ventilation, and also use this unit to do some cooling and de-humidification too.

If you REALLY want "comfort", then a hot water heating system serving some radiant heating floors (or ceilings) can be used, with that air to air energy recovery unit. I'll direct you to www.healthyheating.com for more on the "total comfort system".

Vinnie Smedick

System Design

Mark,

Enough with all this talk. Get yourself a reputable heating/air contractor and go over your options. My call would be to install a hydro-air system. Trash that fuel wasting steam system. The boiler would serve to heat your hot water requirements, heating needs, and any other possible ( radiant floor warming, basement room finish baseboard heat) needs. With the air handlers you not only have the necessary ductwork to accomplish both heating and cooling the conditions in your house, but that opens up more options ( humidification, air cleaning, air changes )so I guess it's entirely up to you what you choose, ask the contractors bidding the job to provide you with some energy analysis of their proposed systems to see which would be most cost effective for you.

Good Luck!