OT question but hopefully you can still enligten

v1rtu0s1ty said:
politics123 said:
There are many types of zoned systems. In my house, I have two units, one for upstairs/one for downstairs. That's two zones.

eg: In other houses, they only have one unit. Within the ducts they have dampers that control the rate and direction of airflow. Your house probably has a central stack going to the upstairs registers. You can put a damper (controlled by separate thermostat) that opens and closes to heat/cool the upstairs separately from the downstairs.
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Looks like zoning can be done even if we only have one furnace like what you just have mentioned guys. That's a good news. However, does having zone more efficent in single furnace house?
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there are two reasons to consider zoning:
(1) comfort
(2) efficiency

Comfort is defined as having your house feel good to you as you use its different rooms. In most houses, insulation is so-so, ducts aren't sized correctly, etc and this causes some rooms to be draftier or colder in winter (or warmer in summer). Common problem: you want a 70 degree house in winter. You set your thermostat to 70, but your MBR is draftier/over the garage/etc and feels too-cold. So, you turn up the thermostat. You've now got a 70 degree MBR and a 74 degree kitchen. You decide the kitchen is too warm, so you turn the termostat back down to 70, but then you have a 65 degree MBR. Zoning tends to eliminate temperate differences on different floors, and depending on how many dampers, can eliminate the temperature differences between rooms on the same floor.

The efficiencies for zoning come from you heating or cooling rooms you need (only) and only to the extent they need to be. In my case, I work from home a couple days a week (my office is upstairs). So, in winter, I have the heat set to 67 upstairs, and 60 downstairs. I'm not downstairs... I don't care if its 60, and I'm saving 56 degree hours (8 hrs * 7 degrees) each day I work from home by not having to condition that downstairs.

You can also save money on annual utility bills by having a high efficiency furnace or A/C, improving your insulation in the attic, etc.
 
I went through this on our new house and had to tradeoff zoning, high efficiency, single/double furnace etc for the Seattle climate (no AC, mild in winter).

I ended up with a high efficiency furnace and no zoning mostly because the cost/payback didnt seem to be there and in our case we didn't have very much room for upsized ducts or second furnaces. If cost was no factor I would have tried to do two furnaces.

An interesting note on this whole heating topic that might be worthy of it's own thread is that in our area we are required to:

1) Use 6 inch framing on exterior walls
2) Thicker insulation
3) Efficient windows
4) Other building prectices to make a more sealed house.

AND

5) Run a 250 CFM exhaust fan, furnace fan for 8 hours a day.

This requires that I have remote control of exhaust fans, interconnect to the furnace, an electrically controlled damper to allow OUTSIDE air in. Effectively a system is created that is like cutting a large hole in the side of my (efficient/tight) house to get fresh air AND I'm running my furnace/exhaust fans 1/3 of the time. Throwing heat out the window seemed un-green to me and I was told I could buy an exhaust heat exchanger that was 80% effient for somewhere between 1-2.5K + install...

I'm tired of this stuff. Don't get me started on the sprinkler system I was forced to put in and the second water line+meter. :)
 
I spoke to the a/c vendor yesterday and he told me that I don't need zoning. 4-ton unit is sufficient enough to cool my house. He told me that the way the airducts were made were really nice. I also have the device similar to yours which brings fresh air from outside and spits out the air inside. It runs like 20mins per hour.

And also, I was able to get in touch with the people that installed and designed our furnace. He told me things that are way over my head. I remember he told me that they just didn't do heat gain/calc, manual j, but they did Rezcalc and infiltration. They also measured the walls, what type of studs they are and R-value insulations. They came up with a 42,000 BTU which should be handled by a 3.5T unit. However, I'm going to up it to a 4-ton because to anticipate hot weather and gatherings. According to the other vendor, adding 20 people load to his software tool, it recommended a 4-ton.

Again, for the zoning, I'm still about it. Good thing is that, it can be done in the future.

So guys, I had a question earlier in my other post. What are the things I need to buy so I can let ELK control my HVAC?

Thanks folks!
 
hucker: I'm about to install my own fresh-air ventilation (HRV or ERV)system. It's a typical "green" project, and while it actually costs money, there are some health benefits --> less carbon dioxide, formaldeyde, radon in the house. With a good filter to remove outdoor allergens, these are nice.

If you tied your fresh-air intakes to the furnace, you're forced to run the furnace a LOT. It's better to have a variable speed fan (a few hundred dollars more expensive for the furnace, but it uses MUCH less electricy to run... if you run your fan constantly, it's like a 1.5 year payback)

As for the ELK, I really am about to do the same thing (I said that in a post 2 weeks ago, but got distracted!!) A serial expander and the HAI t'stats. :) They aren't perfect, and there's some noise about build-quality, but they are relatively inexpensive and are supposed to work well with the ELK.
 
I agree with the health benefits, no problem there. It is the thought of spending extra money to meet house efficieny code, then spending extra money to correct the problems caused by meeting the code.

I'm not sure where the variable speed fan is that you are talking about. We have a 2 speed fan in our furnace, is that what you mean or do you mean a separate high efficiency fan?

I've been thinking that it would make more sense for me to dump our stale/hot house air into the crawl. That way atleast I'd recover some of the heat without buying an exchanger.
 
yeah, the "typical" furnace is 2 speeds -- low when pushing hot air, high for pushing cold air (cold air is heavier). Variable speed furnaces are driven through what's called an ECM fan motor.

NOTE: you cannot swap an ECM for your current fan (I keep on asking, but nobody can do it for me) -- you'd need a new furnace. However, if you're buying a furnace, the ECM motor wholesale cost is only a couple hundred more than a normal motor.

The following is the marketing cost-saver. I think its a little unrealistic, but the return on these is pretty good.
http://www.geindustrial.com/cwc/comfortcenter/engycalc.htm

To give you an idea of extra cost (not that you can find a local contractor who isn't trying to make an extra $$$ off of you), check out
www.wholesaleac.com
The example:
(1) a 95% efficient, 45k BTU, 3 ton with ECM motor: $1234
(2) a 95% efficient, 45k BTU, 3 ton multispeed motor: $873
Net difference: $361

I'd be very hestitant on dumping warm, humid air into an attic or crawlspace. You're asking for mold and water condensation problems.

Do your codes only require an external air-intake, or do they also require an exhaust? If only an intake, you are essentially pressuring your house, which will force warm air into your attic and crawlspace. This isn't good. You need to have balanced system... 250CFM in and 250CFM out.

We've completed our house and are adding a few more features in order to qualify it as a "green-home." I'm likely going to do this myself because I was given OUTRAGEOUS prices from the HVAC folks. For decent prices on the hardware, check out:

www.iaqsource.com

You can get the cheap suncourt for ~$600 and a honeywell in the $800-1000 range. All it really requires is four holes: two outside (in and out) and two inside (supply and exhaust). Anything more than that is a nice to have feature. You may also consider an ERV (that's what I'm going to buy)

EDIT: I think this is easily possible DIY. The pro's quoted me $4500 for the install (GAG!) for what I think is a 4-hr pro job. My tools list:
  • large drill bit (for keypunch into floor and outside)
  • reciprocating saw (or jig saw)
  • two exterior exhaust hoods
  • 6" flex duct (NOTE: You need to get the insulated kind to avoid condensation)
  • a couple of 45 or 90 degree connectors 2x 45 degree adapters are always better than 1x 90)
  • two floor vents (I'm going to put my unit in the basement and vent it to the 1st floor)
 
hey politics,

What do you think about attic fans? I'm seeing different opinions about it. Some say that it will take out the hot air in your attic but say like Tim Silva from ThisOldHouse that attic fans are not good since it will suck cold air from inside the house via holes in walls, etc.

I'm having a hard time deciding if I should put attic fans to minimize cost on my A/C usage.

Any help would be greatly appreciated.

Thanks!

Neil
 
do your own for 50$ . . excellent software . . a snap to use . . did my own house with it as most HVAC contractors use 'rule of thumb' design . . I should know, been doing HVAC sheetmetal for 20+ years . . the design guys were I was working at the time all came up with 4-5 tons . . after using the software I came up with 3.5 . . been in the house 7 years now and the system works like a charm . .

http://www.hvaccomputer.com/

on the order page they offer a 2 month homeowner version . .

https://www.hvaccomputer.com/hvac/secure/HVACOrderForm.asp
 
v1rtu0s1ty said:
hey politics,

What do you think about attic fans? I'm seeing different opinions about it. Some say that it will take out the hot air in your attic but say like Tim Silva from ThisOldHouse that attic fans are not good since it will suck cold air from inside the house via holes in walls, etc.

I'm having a hard time deciding if I should put attic fans to minimize cost on my A/C usage.

Any help would be greatly appreciated.

Thanks!

Neil
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I believe both views could be correct, depending on your situation, however, I think both views overlook the potential that insulation has to reduce your energy costs year-round.

I believe you should use what was designed for your house. If your house needs a powered fan to adequately ventilate the attic, then you should have a fan (and it should already be installed). If your house was designed to use passive ventilation, you should not add a fan.

All attics need ventilation. Most already have some form of it (window, soffit vents, ridge vent, fan, etc). Your house should have been designed with attic ventilation in mind.

My house is completely passive -- it has soffit vents and an attic ridge vent, and no fans. Due to the stack effect, heat rises out the ridge vent and draws in outside air through the soffit vents. Some houses include fans to help cool the attic.

Note that any fan, by blowing air out of the attic, creates a pressure gradient. This forces air to come into the attic -- through the roof, through a soffit-vent, or from leaks in your houses' ceiling. If your house was designed to use an attic fan, the soffits should provide enough make-up air to keep the system in equilibrium. If you install an attic fan on a house not-designed to use it (or a much-larger attic fan than the house was designed for), that make-up air will likely come from your house.

Here's why I think both views are somewhat misleading: Why spend money installing a fan that is only going to be used 3-4 months of the year, and costs you electricity during that three month period, when instead you can improve your insulation (and/or energy seal) and get 12 months of performance increase and not use a single watt?

One thing that you might consider: get yourself an energy-star rater to evaluate your particular situation. They can look at your particular situation and recommend an exact course of action (and predict your actual energy usage depending on your choices)
 
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