View Full Version : New Forced air heat/ a/c concerns due to water heater.

02-01-2011, 07:10 PM
Hello all.

Currently I have an original with home 42 year old Janitrol forced hot air system.

I am looking to get central air, so it makes sense to replace all.
Looking at A/S Trane, and Lennox at the moment and trying to decide which to go with.
So any insite on that would be helpful.

The problem comes with this.
The water heater is fairly new and vents through the chimney along with the furnace.
With the new furnace being direct vent, I'm told I would have to line the chimney for the water heater.
Okay, no big deal, maybe $400-$500 or so it was thought.

Back in 1985 the owner decider to add an additional brick wall and platform for a wood burning stove.
When they put up that wall, they cemented and bricked in over the vent going out and through the chimney.
This being the case, I've been told to put in a liner I would have to bust out part of the chimney from the inside of house to feed over the liner. Oh god, now we are talking 1400-1800 after re-bricking part of the fireplace.

So, the other choice is for the installer to install a Bradford White 40 Gallon Direct vent system.
Since I would have it done at the same time as the HVAC system, he would do it for $1700.

(Since code states water heater does not create enough vent heat for draft type.)

Im stuck because regular vent water heaters are cheap, and will they work without power, etc.
I kind of worry about the direct vent just because of extra things to go wrong.

Most people I talk to say break the chimney out and line it, better in the long run.
That a simple water heater is the way to go and cheaper to replace parts wise and labor wise.

What is your thoughts?

Also any thoughts on the Trane/Lennox debate?

If I missed something to mention, please ask.

Thank for your time.


02-02-2011, 09:33 AM
What does lining a chimney have to do with installing a new furnace? If its direct vent condensing,
run the furnace vent out the sidewall.

02-02-2011, 10:21 AM
A power vent on the WH would let you go out the sidewall, or possibly up to the roof (there are limitations on how far, varies with models). The fans can go before the tank leaks, but it isn't that much more, and would solve that problem. But, what would happen if you plug that now unused section of the chimney? You really don't want an open channel sitting there unused. Not sure what the proper procedure would be, and that might add to the equation on deciding which is better.

As to the brand, both are good. From a comfort level and maximum potential energy, a two-stage burner and a variable speed fan will improve comfort and overall efficiency. Any heating/cooling system works best when it is running constantly. A variable speed fan helps to avoid that cold surge in the winter until the ducts warm up, runs longer and has less wind chill effect unless it really needs the full speed (which it ramps up to and may never use). The variable speed during the cooling season lets the thing extract significantly more moisture out of the house during the startup and shutdown periods when it runs the fan slower. This lets the air linger a little longer through the cooling coil and therefore extract MUCH more moisture per pass. Now, if you live in the dry desert, this isn't an issue, and maybe a detriment, but for most of us, it will make it feel much more comfortable at a higher temp since the air is dryer. There is some truth to the 'but it's dry' issue you hear from those in the hot dry desert...you can tolerate higher temps if it is dryer more easily. Proper sizing is also crucial, as oversizing will be more expensive to buy, run, and have lousy comfort.

02-02-2011, 11:19 AM
Right now, my chimney has 3 flu's (sp?).
One for the water/heating, one for the wood stove and one for the fireplace.

The chimney has a screened cap on it, so I don't think I am too woried.
We were going to cap it off in the furnace room if I replaced both the heat and water.

As far as the Lennox model goes, it was the Signature Collection for heat SL98V which I think is top of the line residential. Variable Speed motor and Variable-capacity operation for heat stages.
For the A/C still Signature Collection, but thinking mid range, because to go one step up from XC17 to XC21 it was $1600 extra. Many argue it would take forever to make the money back in savings and since the house is only about 1600sq ft living space it may not make a differance. 3Ton heat and 2.5ton A/C if I remember for the forced air systems.

In total, I was quoted $9800 for the Heat and A/C soup to nuts.
The power humidifier to replace the old drump one was an extra $460.
Finally the Water Heater was another $1700.

All prices included permits, electric, pump and lines to drain into washer drain half way across house, top of the line iComfort Stat just introduced.

If I were to go best A/C it would pump it up another $1600.
If I didn't have to replace the water heater, I would have concidered it.

The Trane stuff was about the same spec's and a little less money, so that was a wash.

There are some good rebates, but still a lot of money.

Thanks for your input.


02-02-2011, 11:24 AM
I shoudl have added on the Lennox A/C XC17 and XC21 the only difference I see was up to SEER 17 and SEER 21 respectively.

Also the XC21 was two stage where the XC17 was not.
62db versus 69db so XC 17 a little less.

Warranty on all is still 10 years.


02-02-2011, 12:21 PM
To answer your question, according to code, I can not just have my current water heater venting through a clay liner.
Not enough heat from the exhaust of the water heater causing condensation and other problems.
It would have to have a aluminum or stainless liner installed.

What does lining a chimney have to do with installing a new furnace? If its direct vent condensing,
run the furnace vent out the sidewall.

02-02-2011, 04:18 PM
SEER is an acronym - and the higher the number represents higher efficiency. Depending on your utility costs, it may never pay back to get the bigger unit.

But, 1600 sq ft may be too small for a 3T unit. The worst thing you want is an oversized a/c unit. Do not buy anything until they run an analysis on YOUR house, using the widow size, placement, type, insulation amounts, building orientation, and factor in how well sealed it is, then equate all that to the normal temperature and humidity levels and determine your 'design day' worst case. It is not uncommon to avoid this and end up with a unit that is way oversized. This compromises comfort and economy. If in-between sizes, you might opt for the smaller one unless you reach that design day temp often. For example, you might have a once in 10-years where it gets to -10 degrees, but the 'normal' low is 5 in any given year. You might not want to design it for -10, because it rarely not only reaches that temp, but it doesn't stay there forever. If the house was at your desired temp during the day, and it only got to that super cold temp early in the morning, it wouldn't have been steeping in the super cold very long, and you may never notice. Same with the a/c size. If the a/c is running constantly, drying the air, and you go 5-degrees over the design temp for a couple of hours, you may never notice. It's when it stays there for a long time, or you shut down, then want to cool a very hot house where that extra capacity comes into play. But, once it does reach the set point, it only needs to run a very short time...that creates cold, clammy conditions, not very comfortable.

02-02-2011, 04:42 PM
The old heater is original at 42 years old.
100,000 BTU in and 80,000 BTU out.
80% efficient I guess.

All contractors who have come in have estimated 61k-66k BTU at ~98% efficient.
They all also said 2.5 ton a/c.

I said 3 ton heat, because that's what I translated from the part number ending in 30 for size.

The house was built in 1968 and is very loose.
I've seen what was in the wall, tin foil with papser backing. About R7 from what I've heard.

Some joker put up basement walls with studs facing flat with no insulation and paneling.
So, I am working as I said with a loose house.

02-02-2011, 05:08 PM
Make them show you how they calculated that! Using square feet alone is NOT going to work. Your old furnace could have been 3x oversized or more. Unless on a really cold day in the winter it never shut off and the house got cold, it's probably oversized...how much is the important factor.

02-02-2011, 05:14 PM
Thanks for the info.

One of the guys (older seasoned) had graph paper, drew out the layout and we spoke of how the house was insulated newer windows, etc.
This guy was well recommended seemed to know what was going on.
Days later he came back with a quote.

The other guy did similar and they were both within' a like 3k BTU and more or less close in price.

The also mentioned neededing an additional return which was included in price.

The others I didn't bother with because they were offering lesser models at a much higher price, but with similar findings.

02-04-2011, 02:57 PM
Where is this house? (got a ZIP code?) How big? A 60K+ peak load is pretty high for a modest-sized home in most of the lower-48 of the US. You may be able to buy a lot more comfort with an air-sealing and insulation upgrade along with much-downsized HVAC equipment. (The 60-65K number "feels" like an old schoolers, "Lessee, we have this house with newish windows, but it's pretty breezy with junk insulation- can't be the usual 25 BTU/foot, so lets call it 35 BTU/foot, times 1600 feet is..." which is almost always at least a 2x overestimate.)

Homes with R7/R8 econobatts with foil facers were pretty common in parts of the US with 4000 heating degree day climates back when energy was cheap, but even then I'd be surprised to see 65K peak loads in climates that mild, even for a leaky barely insulated house with bare-minimum double-paned windows (or single-pane double-hungs + storms.) Most of time it's pretty easy to retro-fit blown celulose/rockwool/fiberglass into wall cavities with econobatts and literally double the R-value. (If cellulose youll also reduce the air-infiltration 90%- more if "dense packed".) No matter where you live, the comfort factor will be higher both summer & winter by boosting the R value and tightening up, even at the same room temp. 50F walls just plain suck in a drafty dry mid-winter. Even if the air temp is 70F, you feel it, just as you'd feel the heat radiating off 85F walls on a 100F day in the same house in summer even though the air in the air-conditioned room is 75F.

I currently live in a ~2000' antique (with another ~1500' of semi-conditioned basement) that came with NO wall insulation, and ~ R5-R15 of rock wool in the attic (different, in different parts), in a ~7000 heating degree day climate. Even before insulating and air sealing, my (measured, with the boiler) heat load at 0F outdoor temps was around 45K. Most of the windows are the original, installed in 1923, but with storm windows on the exterior. I'm still working on the place, but with retrofit celluose in most of the walls, some air sealing, and some upgrades to the attic insulation the peak heat load is now hitting around 30K. By the time I'm done it'll be ~25K, less if I swap out the windows.

An atmospheric-drafted hot water heater (like any open flue) is sucking air 24/365, increasing the heating & cooling loads, drawing dust pollen and humidity in at random locations. Sure, they work without power, but so does an earthenware pot on an open fire in a cave, eh? Unless you live in a place with truly abyssmal power reliablity issues, pretend this is the 21st century, seal up any unused flues (and use good flue-dampers on those you do), and get the direct-vent unit. If the power goes out you'd still have at least SOME hot water over the next couple of days if you use it sparingly.

If you have some heating-season gas bills with exact meter-reading dates, we can look up degree-day data for your location and come up with a pretty accurate heat-load number based on fuel use (unless you supplemented with a wood stove or something) for the house as-is. Using that number for an upper bound, a 2-stage gas furnace would still run pretty efficiently even if you decide to tigthen & insulate.

02-04-2011, 03:13 PM
Thanks for taking the time everyone.
Hey Dana, thanks.

The house is raised ranch ~2000 sq ft with the garage (also R7 I think) underneith two of the 3 bedrooms, so let's call it 1750 sq ft living area. The house is built on a slope, so half the height of the basement is underground.
I'm in the Boston, Ma area zip code 01701. Newer Newpro windows that I think they failed to insulate around before they put back together. (Feel nasty drafts in places.)
The attic had additional insulation added, but the idiot used craft faced insulation plus the original, so I have to rip it out and do it right. (No floor in attic. Ridge and soffet vents exist.)
The craft paper facing the cold zone is black now. (So it was R7 faced plus his faced R18 in many places)
When I do insulate the attic when my busted leg heals, I will have R19, plus plan for another layer with R38.

Below you will see the Therms #'s seem pretty consistant in January. We've also had 4 big snow storms recently.
I have Forced hot air gas, gas dryer and gas water heater. (Stove is electric, go figure.)

If you really need it, I have some CAD type drawings I did with all layout. I could update with vent locations of necessary.

While I have a fireplace and wood stove, I don't use either.

01/18 158

12/18 122

11/18 68

10/18 30

09/17 19

08/18 17

07/20 23

06/17 22

05/19 46

04/20 70

03/19 106

02/18 132

01/19 158

02-04-2011, 03:22 PM
One other thing I should have mentioned is that the bedrooms over the garage are at the opposite end of the house.
Those vents don't get much airflow coming out of them.
I've tried messing with the vent's around the house but not much differance. Even tried wiring the blower from medium to high.
While it increased the airflow, the humifier couldn't keep up, so back to medium it went.
All the dampers closest to the furnace in the ceiling are covered with drywall, so I can't adjust those.
Every bedroom has a return with one bedroom having two output's. Perhaps that's what they did to get more heat at that end.
There also in a double return where the living/dining/kitchen/hallway meet.
Finally, one more return in the basement near the furnace.

The contractor was planning to add one more return downstairs where another was thinking upstairs.
(Not sure who is more in the right.)


02-07-2011, 09:21 AM
Looking at the last 12 months and doing the annual average (to get around the 1st of the month boundary error using http://www.degreedays.net/ , using weather station KMAFRAMI2 ) you had ~6169 heating degree days, in which you used 813 therms, or 0.132 therms/HDD of source fuel. Assuming a system efficiency of ~80% that means you're using 0.8 x 0.132= 0.106therm/HDD, or 10600 BTUs/HDD To figure out an hourly rate: 10600/24= 442 BTU per heating degree HOUR. Outside design temps for Framingham are around +5F, which is 60F less than the 65F baseline, so the "right sized" output for the furnace need not be greater than...

60 x 442= 26520 BTU/hr ...

to keep up. This is credible- my place in Worcester has less attic insulation than yours and likely leakier windows, with a similar heat load at +5F. (To hit 60-65K for design-day heat load would mean that it needs more than twice the BTUs than is available in the source fuel!)

This is a max, since a fraction of the total is presumably or hot water/cooking, etc. and the thermal efficiency the older furnace is likely less than 80% after 42 years of service, and the tigthness of the 42 year old ducts is also probably less then perfect, etc. It's also at low end of output for most 2-stage furnaces. For comfort, efficiency and maintenance reasons ideally the low-stage output of an modulating or 2-stage furnace would be under our calculated 26.5K number.

If you air seal to under 3 air changes hour at 50 pascals (ACH/50), (which may be possible if you seal up the abandoned flues) you will in all likelihood not need to add humidity to keep it above 30% RH, and it'll probably knock on the order of 10% off the peak heat load. If you use blown cellulose in the walls to raise the R of the walls that'll likely be another low-double-digit improvement, so looking forward you may be under 20K for a design-day heat load.

A problematic insulation area on many raised-ranch designs is a cantilevered overhang that makes for either a cold-spot, or a condenstion/rot area if batting was just stuffed in there with little attention to air & vapor sealing the inteior between the joists (which can be difficult to do.) Sometimes this can be insulated with dense-packed cellulose blown in feed-bags stuffed through holes drilled on the unederside from the exteior, but if accessible from the interior it's better if you gave it a 1-2" shot of closed cell foam on all exterior wood first.

If the kraft facers in the attic are on top, that forms a semi-impermeable condensing surface on the cold side of the insulation, which is what's causing the issue. As long as it's not actively moldy you may be able to re-use them by flippikng them facer-side down, which puts the vapor retardent facer at a warmer layer that will stay above the dew point of the interior air (typically 37-40F) for the larger fraction of winter hours (assuming those batts are 50% of the total R.) But wether re-used or replaced, you'll be better off using blown cellulose rather than batts, since batts perform at lower than rated R at the temperature extremes due to convection within the insulation (whereas cellulose retains R) , and batts are nearly impossible to install without performance robbing gaps & compressions. Even though code-min is R38, taking it to R50-R60 is still cost-effective from a fuel consumption point of view (especially if you get the MassSave kickback from the utilty), and from an ice-dam prevention point of view. Also key is getting/keeping the R value up at the soffit edges under the slope of the roof where it may not be deep enough to do all with low-cost fiber, with judicious use of rigid &/or closed cell $pray-foam insulation. (If you have a truck and want to do it DIY, buying recycled rigid foam from The Insulation Depot (http://www.insulationdepot.com/)on Waverly Street can be cheap. Using R12-R20 rigid board on the rafter edges from soffit-to ridge seald at the seams & edges preserves the roof deck venting and can make air-sealing the ceiling less critical.)

But before insulating, air-sealing all plumbing & electrical penetrations to the attic is an important first step, either as a DIY or by a pro. (An insulation company that specializes in air sealing as well as insulating (http://www.theenergyallstars.com/) may be the right way to go if you want to take it all on in one go and be done with it.)

02-07-2011, 10:01 AM
Wow Dana, that's a ton of info.

Thank you for taking the time.

I have to decrypt some of the info you have provided, but it's all good.

You hot the nail on the cantilevered area, although I can only get to a small area of it due to finished ceilings.
The previous owner of my home and the neighbor both had the siding done at the same time.
Differance being the neighbor did blown in and soffit venting at the same time.
I had snow and rain (Joy!) in my attic the first year and after new soffit venting, it hasn't happened again. Makes you wonder why he didn't do it at that time.
Now it will cost a lot more money that it would have had it been done right the first time.

The thought was ripping up the old R7 and R19 in the attic and start fresh, however that's a lot of trash to get rid of.

We do use the attic as storage, so I will have to make some sort ot stands or hanging shelves with the extra insulation.

As far as humidity, it was never a problem until I got married when my wife moved in and demanded more heat! lol
I think I finally got the humidity square after fixing a slightly broken Humidistat as well as final adjustments on vents.
Speaking of, I wish the ceiling wasn't up so I could better adjust the inline governors.

Thank you again for taking the time with your extensive info.


02-07-2011, 11:59 AM
Blowing cellulose over old batts isn't a problem if they're not moldy-stinking full of mouse nests or something. A top-cap of cellulose "fixes" the inherent convection loss issues with low-density fiberglass. To get R50 you need at least 14-15" from the ceiling-gypsum to the top of the insulation. The weight of the higher-density overblow will compress the batts a bit, but as long as it's 15" deep on day 1 that will be your approximate R value. To hit R60 you'd be looking at ~17-18", which may be tough to do at the soffits as the roof deck slopes in. Rigid-board iso runs ~R6-6.5/inch of thickness, so even with 2x8 joists it's usually possible to stack in some iso to keep the R-values up to at least R40-R45 right up to and over the top plate of the studwall, whereas with batts or cellulose it might thin out to less than R30 at the ends, which will rob overall performance, and increase the ice-dam risk. With typical eastern/central MA snow loads and temps R50 is enough to prevent big ice dams from forming unless you have big heat-leaks from flues, plumbing vents, skylights, etc. (This year has been good test, eh?)

R38 can even be enough to prevent ice dams if it's installed perfectly, but during cold snaps R38 fiberglass is performance is less than R30. The cost of even a 3" overblow of cellulose on R38 fiberglass is worth it, since it raises the cold-weather performance by nearly a factor of 2, even if it only improves the April performance by 25% or so. By filling in all voids & leveling out compressions it raises the true performance by more than what might be implied by the rated-R values of what was added and what was already there.

A clever insulation contractor can usually insulate the cantilevered sections adequately attacking it from the exterior rather than in interior, with low overall mess & repair. In some instances it might be worth going with slow-rise "half pound pour" foam since it seals better than cellulose, but cellulose blown into feed-bags to keep it from filling up the entire joist & ceiling bay is a tried-& true methodology as well.

Air sealing contractors typically run a calibrated blower door to come up with a ACH/50 numbers both before and after air-sealing, and will usually guarantee some minimum fractional improvement. The more you can seal the big and obvious leaks yourself (like abandoned or undampered flues), the better value you get out of them. Some will use infra-red cameras to find more subtle leaks during the initial blower door test, by de-pressuring the house and looking for the cold spots, then spin the fan the other way to pin-point the leaks using a smoke-pencil. The latter you can do yourself with a stick of incense and a window fan. If you're really into it you can buy a $75-100 pistol-grip infrared thermometer and find the cold-spots indicating leaks with the house de-pressured, but it's a lot quicker/easier with an IR camera (which is essentially unaffordable for a DIY-er) than a thermometer.

I hope your leg heals quickly (and I hope it wasn't from falling off a ladder while cutting some channels in ice dams, as happened to an acquaintance of mine on Saturday... :-( )

On the remote bedrooms, make sure it's not the returns being blocked, it may not be a supply duct problem at all. In many older homes the returns are commoned in a hallway or something, and if the doors are closed the "return" is via the great-outdoors through whatever infiltration leakage you have. If that's the case here it may be possible to use a partition wall cavity as a return path, with a grill at the bottom of the cavity on the room side, and at the top on the other side. If the air flow to the remote bedrooms continues to be an issue with a right-sized furnace and additional insulation, with a heat exchanger and some plumbing it's possible to use your hot water heater as a heating boiler to run baseboards or small radiators to heat those areas.

02-08-2011, 03:39 PM
My joists are 2x6 I believe, not 2x8, but I plan on R19 and probably an R38.
I've debated on the blow in iso, but it's something I'd have to hire out and I'm not sure the cost differance.

Thanks for all your time, you've been more than patient with me. lol