New Construction HVAC decisions. Geothermal vs. alternatives with upgraded envelope.

[kenmac]

skip all the duct work and go VRF. You can supply multiple inside units from one outside unit, and there is no loss of air flow, heat, A/C through the duct work. In fact, no duct work at all !
Some are good for 80% capacity @-22 and 100% @-4 deg which depending on your heating needs, could eliminate the need for any back up heat

 

[Raspy]

One of the things I've seen over and over is the forced air guys want to add a backup system "just in case". One of the justifications for this is that the radiant system takes so long to heat up, or may fail. Of course, this argument is being put forth by someone who knows nothing about radiant and wants to sell more equipment. It often works. But later, when talking to the homeowners they eagerly say they never use the forced air and don't like it. Or they simply say the radiant is their favorite feature of the house.

In this case there is already a backup system. A fireplace. It may not be the first choice, for a number of good reasons, but it works and requires no power. So, it may be possible to reduce the cost of the forced air system and get the radiant on line in the beginning.

 

[newbury]

Thanks. Very help as usual. I�･ making it a point to have great air sealing to help cut back on infiltration. We are using ZIP, and the NuWool is a damp spray that gets put in AFTER all seams and penetrations have been sealed. Part of me feels this should be more than sufficient, but I also worry about thermal bridging.

I�･ going to have all utilities placed in the basement central located for what it逞ｴ worth.

I just get frustrated because we live in a è*�熔w tech area where I feel like most of the subs are used to building what they豎*e used to and scoff at the newer ideas (like the use of Manual J逞ｴ to properly size an HVAC system).

My GC is great about staying up to date with current building methods, but in the areas he subs out, I�･ finding even his good subs don� know all I want them to know to complete some aspects of the project.

When I�･ paying the bills, and I want my house to perform a certain way, I�･ going to be extremely disappointed if it doesn� because some sub didn� or couldn� bother to stay up to date on proper building science.

You write like an educated person. I've lived as an adult in Northern Vermont, Virginia and Mississippi. I own land and have hired contractors in all three. I think it is pretty universal that most GOOD contractors don't like to experiment and use the latest building science unless it is a sure kill. It's usually more expensive to come back and fix something than to put in something you know will work.

What is your target room temp for heating? Some people need it at 73 degrees F. Others can live at 65. I set ours at 60 for the winter, that's what we like. I don't turn it down when we leave the house unless we are going to be gone for days. (And for the cooling I used to set it at 80, then 78, but the wife revolted and now 75 is the compromise.) But if you design a system for heating to 73 it will probably be cycling it too much for 60.

I'd strongly recommend against going with 1 "system", put in a woodstove for when your motor fails or something messes up on your main system.

 

[JamesHW]

We’re dealing with decisions for installing a heating system from scratch, although in our case it’s retrofitting an 100+ year old Upstate NY seasonal brick house last heated with coal stoves. GeoThermal with horizontal loops was an early fav but has faded from consideration somewhat. Research showed sand, while one of the best conductors when wet, is one of the worst when dry. The house has a massive chimney in the center, but a fire that burned the roof off, we think in the 20’s (family stories are vague). In any event the solution we end up with needs to be workable for my wife if she is alone, so wood burning stoves are low in our consideration. No chance of pushing air through ducts from a furnace unless we go with a high velocity tube system, but generally impractical & expensive. Low profile radiators mounted on exterior walls under the windows and a furnace in the basement seems our best play, maybe supplemented with electric fireplaces that take advantage of the two sided fireplace (kitchen & front parlor). In any event we’re starting by sealing up the house and insulating the attic as best we can and moving forward with good, double paned storm windows. We also have an 800 sq ft wood 1 story uninsulated wood addition to consider, but figure short term a good old wood stove would work best and any central heat considered separately from the main house. Perhaps by the time we get to that phase their will be some new options to consider.

Didn’t want to hijack the thread, but I always learn something new. Thanks!

 

[jk96]

Old school tip... 600 sqaure feet per ton, and if the load calc don't come up to that, you missed something:laughing: In all seriousness, part of the reason for the load calculation is to help determine the duct size per room to room.

I think my HVAC guy used the old school tip. That's why I ended up with 8 tons when I needed 4-5 at most.

 

[MGH PA]

You write like an educated person. I've lived as an adult in Northern Vermont, Virginia and Mississippi. I own land and have hired contractors in all three. I think it is pretty universal that most GOOD contractors don't like to experiment and use the latest building science unless it is a sure kill. It's usually more expensive to come back and fix something than to put in something you know will work.

What is your target room temp for heating? Some people need it at 73 degrees F. Others can live at 65. I set ours at 60 for the winter, that's what we like. I don't turn it down when we leave the house unless we are going to be gone for days. (And for the cooling I used to set it at 80, then 78, but the wife revolted and now 75 is the compromise.) But if you design a system for heating to 73 it will probably be cycling it too much for 60.

I'd strongly recommend against going with 1 "system", put in a woodstove for when your motor fails or something messes up on your main system.

Target temps probably would be around 72 in the winter and 68-70 in the summer. I would definitely want our master on a separate zone since we sleep with it cold all year long.

We will definitely have a wood stove, I just don't want to rely on it for primary heat

 

[EddieWalker]

I think it is pretty universal that most GOOD contractors don't like to experiment and use the latest building science unless it is a sure kill. It's usually more expensive to come back and fix something than to put in something you know will work.

Solid advice. With the government getting involved in Green Energy, and subsidizing so many "new" technologies and methods, it becomes very difficult to know which will work, and what is just a fad, or even worse, a method to get Federal Funding. This is especially true with Solar and Wind technology. You don't know what you are getting, how long it will last, and if there will be somebody that will even work on it in ten years. I've seen this with plumbing more then anywhere else, but I don't do HVAC, so I can't say how many "experimental" systems are out there that people will regret having down the road. How many people fell for the pigtail light bulbs that where supposed to save so much money and save the environment?

 

[NorTracNY]

Am I gathering it correct that you're looking at geo, but not do radiant floor heat? I understand the radiant heat is a little more expensive (labor cost is a little higher), but with new construction, I'd value the radiant heat over geo. I was lucky and learned about radiant heat before we built. Definitely one of the best aspects of my house. You'll save money long term as you will not set your heat as high and it's more efficient.

 

[Raspy]

Target temps probably would be around 72 in the winter and 68-70 in the summer. I would definitely want our master on a separate zone since we sleep with it cold all year long.

We will definitely have a wood stove, I just don't want to rely on it for primary heat

I always design the Master with a separate thermostat too. Including the Master Bath is a bit more of a decision. If it's a large room, it can get it's own. But if it's smaller it can be with the Master and just regulated to get more heat by proportion. Then a programmable thermostat will bring it up to temp before you get up. The tile floor is the issue. If you don't have radiant heating, the Master Bath can get an electric radiant mat under the tile with it's own floor sensing thermostat. Floor sensing allows a small radiant zone within a larger forced air zone, with no thermostat conflicts. And it allows a cool sleeping area with an inviting warm bath floor.

 

[PEJ5]

There have been some great comments. We just built a garage/2nd floor "cottage" and so far the shell is up and closed in. Work on the inside will start once temps get above -18C/0F.

It was built with 2x6 on 24" centres so the there is lots of room for R22 or R24 batt insulation. Thermal bridging is still a big issue because there are a number of structural locations where 3 or 4 2x6s are nailed together, and headers that dramatically reduce the opportunity to insulate well. Based on how hot and cool you plan to run it, definitely add 2"+(R10) foam outside under your siding. Big payback, and it moves the dew point for any moist air leakage outside the framing to reduce the chance of rot. 25% of heat loss is through the basement walls so again, insulate well outside and below the concrete walls and slab while you have the chance.

As for ceiling fixtures on the top floor puncturing the vapor barrier, strap the ceiling with 2x3" or 2x4" and keep your wiring and boxes below the vapor barrier. There are many ideas for passive solar house construction that can be used to improve your construction.

In 25 years when energy cost are through the roof you will be laughing all the way to the bank.

Finally, I agree that even good builders shy away from new ideas. Share your list of specialized techniques; insist on the big ones and then be prepared to leave one or two on the table.