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Heating & Air Conditioning

Dual Zone HVAC?

10 years ago

Hi all-
I am about to begin finishing a basement in a 1900 sq ft ranch house. We live in Wisconsin so the basement is always about 10 degrees colder than the main level.

I'm considering adding a dual zone to our existing hvac system, which has a Lennox G51MP furnace. The goal is to use the second zone in the winter to make the basement more comfortable. In warmer seasons, there's really no need for the second zone because the basement is cooler and therefore more comfortable, as long as we run the dehumidifier to keep moisture under control.

Any opinions about whether the second zone is a good idea or not? Is my furnace adequate to run both zones?

Thanks very much for any input!

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Comments (7)

DreamingoftheUP
10 years ago
I'm in a similar situation - 50's ranch, around 1200 sq. ft, in the Chicago area. When I finished the basement, I put it on a separate zone, although I have hot water heat. The finished area is very pleasant. Most of the homes in my development have forced air and many of my neighbors ignored the heating aspect when remodeling the basement - they just cut a few holes in the ductwork for the basement. Their basements are usually not warm enough in winter.

You should get a good HVAC guy in to take a look. Maybe your furnace is sufficient or maybe a separate one should be installed for the basement.
mike_home
10 years ago
Having a zone for the basement is the best way to control the temperature. In general it is a good idea.

A basement has very little heat loss, so it does not take many BTUs to raise the temperature. Do you know the size of your current furnace? In all probability it should be able to handle the needs of the basement.

You furnace is a single stage. There is a potential problem of trying to heat the basement zone with a furnace that can only run at one speed. It could be made to work if you have the proper size supplies and return. You need to find a HVAC contractor who is good at zoning (most are not) to determine how to properly set up two zones.
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it takes more than adding blue board on the exterior of walls to make a house tight enough to require make up air. however, getting a house tight enough to require make up air isn't a bad thing. in my world..we call that build it tight, ventilate it right. if the house tests (with a blower door) below a certain amount of air changes per hour, then ashre 60.2 ventilation strategy is used to determine how much fresh air is needed. zoned systems are not achieved with multiple systems. zoning is one hvac system with multiple t-stats that control motorized dampers at the plenum of the unit. you should still be able to do that, if the hvac company has installed zoned systems in the past. if the ducts are designed well, there should be no problem with multiple stories. duct design & sizing of ducts should be done prior to install. I don't get the bit about additional wrapping of ducts. R-value should be R-8 all ducts, plenums, and supply boxes should be mastic sealed. also all recessed lights should be ICAT. insulation contact air tight. then it doesn't matter if they are in between floors or in attic. one of the benefits of building better..and foam sheathing to exterior is a definate better thing..is that hvac systems are downsized. do you have a load calculation for your new build? also is the goodman 13 SEER? if so you may want to invest in more than just the lowest efficiency manufactured. I'm sure they will change whatever you are willing to pay the upcharge for. best of luck.
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Is the master on one end and the furnace on the other of the 80 feet length. Insulation or lack of it comes to mind. If you have airflow, is it as warm as the other areas. I mean if your ducts weren't insulated well, then the air might be cold be the time it travels so far. Maybe an electric baseboard is the way to go. I mean if you are using electric resistance anyway and you have one cold room, the baseboard heater would be the cheapest way to remedy it. Won't help with a/c if that is also a problem - is it?
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Has any contractor done a load calculation? It is difficult to tell from your posts whether the sizes are correct. 160,000 BTUs for heating, and 4 tons for cooling seem big, but they could be correct. Did you ever get accurate area dimensions for the first and second floors? Why the XV80 and not a XV95 for the second floor? Is it a cost issue?
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I suggest separate systems for the first and second floor. That is the best way to have even temperatures on each floor. It costs more up front, but you potentially have lower operating costs. You could zone the loft off the second floor system. However if you are going to be working 10 hours days with multiple pieces of equipment generating heat then spend the money on a mini split.
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cbailey31
Original Author
10 years ago
Hi Mike-
My furnace is a G51MP-36B-070. Does this tell you anything about the size?

My intent is certainly to check with an HVAC pro but wanted to go into the conversation with enough info that I feel somewhat informed, knowing there are some contractors that are not necessarily good at dual zone design. I don't want them telling me this will be no problem if their design will not work with my particular furnace.

Any further input is much appreciated.
mike_home
10 years ago
This appears to be a 70K BTU furnace (62K BTU output) with a 3 ton blower. It should be sufficient for a 1900 sq. foot house and basement, but the contractor should verify this.

What is your location and what are your average low temperatures? Have you ever had problems keeping the house warm on the coldest days of the year?

Here is a link that might be useful: G51MP furnace
cbailey31
Original Author
10 years ago
Hi Mike-
We're in South Central Wisconsin and our average in the coldest months of December and January is a low of around 10 degrees, high of 30 degrees.

We have not had any issues keeping the house warm enough, though we like to keep it around 68 degrees, not a whole lot higher than that in order to keep the bills reasonable.

Thanks again
ionized_gw
10 years ago
Is this a fully underground basement or walk-out? Is there any heat in the basement now?

Is the basement one big room or are there partitions?

This post was edited by ionized on Mon, Feb 10, 14 at 18:57
ionized_gw
7 years ago
This has to be the clumsiest example of forum spam that I have ever seen.

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