Heat Loss calculation discrepencies

frank_31

I am unfortunately still having problems with my heating system in my newly constructed but uninhabited home. I recently had the opportunaty to speak to the heating rep that figured the heat loss calculations for my house. I asked him how he came to a number that was almost 14000 btuh less than what i and several other heating professionals had come up with for a certain room in my house. He advised that there are different heat loss calculators out there and that they all design systems differently. He basically told me that the 14000 btuh difference was the result of him designing my system as "tight" since it was a new house and all the other calculations must have been for a looser system. He then advised that he designed my house to be 80deg. F at 0 deg. F outside. And when I did my own calculations for my house I only did them for 70 deg F. and I believe 10 deg. F outside. So what gives here? Is there really a possiblity that myself and the other heating professionals(including a rep for weil mclaine) can be that wrong? Or is this guy just trying to save his own skin, since he provided the recommendations for baseboard in my house to the contractor? All of our findings come down to he did not recommend enough baseboard for the room inquestion and it will not heat up and when it does thru direct sun light thru the huge windows, it will not maintain the temp after dark on a 30 deg and below night.

I appreciate any feedback on this that you guys can provide. I am just a very frustrated new home owner that wants to get the system right in my house so I can move in seeing how its sitting there finished other than this problem since feb. 10th. I don't want to start an argument here and if the rep that designed the system reads this and would like to talk again he can reach me thru the contractor.

Thanks
Ray

Jimmy Gillies

Ray

Here in the UK, as I'm sure is the same in the US. The design is based on the coldest day(-3Deg C external temp for Scotland).
It sounds you may have a lot of glass in that room, so if it's a south facing window(solar gain), that must also be considered. We are talking a lot of factors to be considered when trying to get the optimum heat loss calc temp for that room, so take it easy on all involved. My advice is have a meeting with the Heating guy/Contractor, the Rep & the GC on site. Give them coffee/cakes and talk it thru. I'm sure you'll get something resolved.
Talking is cheaper litigation.

I hope that's some help?
Regards.
Jimmy Gillies.

Ted_9

Ray

Sound advice from Jimmy Gillies.

Ray, do you have the heat loss for the room in question? Do you have a few differant versions? How much baseboard is in that room? 14,000 of is quite a bit of B.B. Are there cathedral ceilings? Lots of glass?


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don_95

Its fairly

simple if that ok to say.You both should get together and
compare notes.

You know like I'll show you mind if you show me yours.

Yes it true if he allow for a tighter home and you did not then there will be a big difference with the btu losses of
the home.

To quote BOB,lets get together and feel allright>>

frank_31

actually I have had a meeting with the contractor, who is my GC, the heating rep that designed the system, and the plumber that installed it. The meeting was fruitless. Rep wants to blame everything that was not part of his design or his responsibility. the plumber advised me he originally sized the system for roughly 51' of BB and was told by the heating rep that it should only be 33'. the room inquestion is a livingroom that is 19'10" long by 25' wide, with a cathederal ceiling that is 20' high. it has a 12/12 pitch and the front wall(south facing) is about 75% covered by glass(marvin integrity windows). the heatloss for the room from the rep shows an 18600 btuh loss and there is 33 ft of BB in the room. I, along with the others, figured approx. 58+ feet of BB to cover this room. I even went so far as to order the Slant/Fin heatloss program and design the system to the best of my knowledge. I came up with about 59' of BB at 180deg. f.

I have tried to work with my contractor but he won't even listen to his own guy(who's father is a heating professional) about this. He is relying on the rep's information solely. I just wanted to know if there was a possibility that there could be roughly a 14000btuh difference from one program to the other when it is for the same room. I have used calculators that I have found on the net and also information from other heating guys. I by nomeans want to start an argument about this or to sound like I am a professional. I am just frustrated and am looking for some answers.

Thanks again for any input on this.

Ray

Ken_8

Being an instructor for

I=B=R schools where I teach how to do heat loss calculations to those who "need to know," gives me a ton of resources on this topic.

First, there is some diverse ways to do heat load calcs. None would result in more than a 5 to 10% difference in actual HWBB (hot water baseboard) installed.

The Slant Fin software mimics the I=B=R method I teach and is based on ASHRAE standards and values - all of which are universally accepted as sound engineering.

Variables that come into play that can cause "confusion" or less than perfect results might include the following:

1) The louver (small movable blade between the front piece and wall lip) position is critical. The blade must be as vertical as possible. A closed "blade" will reduce output by 50%!

2) For the HWBB, we typically determine output by using the 180° avergae water temp output table. To actually get 180°F output, boiler water temperature must be 190° average output. With the typical 20° differential on the operating aquastat, the limit must be set to 200°! If it's set at 180°, you'll be cold on a design temperature day.

3) Assuming only that one room is cool, it is imperative that the walls, floor and ceiling insulation is exactly (or more than) what was specified!

4) Many times wall to wall carpet is installed. In cases where the HWBB was improperly installed flush with the sub or finished floor - and wall to wall with underlayment padding installed, the air slot under the basebaord is "choked" off by the padding and carpet, effectively blocking the slot and blocking/impeding air flow. This blockage will reduce heat output in the same manner as closing the louver at the top. 50% reduction in heat output.

5) If the pipe size, circuit length and or circulator are improperly sized - the dT accross the loop will be excessive - resulting in a cool room.

Start looking at these five items. If any hit a nerve, post a response and we'll help you "fix" what's broken.

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Tony_8

sounds like

"Pass the buck" to me. You need to get, and be, tough.

You paid for a PROPERLY operating system, right ? It doesn't matter who says what, or who blames who, you are living with an underperforming system for whatever reason. The contractor you paid for this is responsible, period. He needs to take it any further than that, not you. It's time for someone to buck up and fix it.

toearly_2

> actually I have had a meeting with the

> contractor, who is my GC, the heating rep that

> designed the system, and the plumber that

> installed it. The meeting was fruitless. Rep

> wants to blame everything that was not part of

> his design or his responsibility. the plumber

> advised me he originally sized the system for

> roughly 51' of BB and was told by the heating rep

> that it should only be 33'. the room inquestion

> is a livingroom that is 19'10" long by 25' wide,

> with a cathederal ceiling that is 20' high. it

> has a 12/12 pitch and the front wall(south

> facing) is about 75% covered by glass(marvin

> integrity windows). the heatloss for the room

> from the rep shows an 18600 btuh loss and there

> is 33 ft of BB in the room. I, along with the

> others, figured approx. 58+ feet of BB to cover

> this room. I even went so far as to order the

> Slant/Fin heatloss program and design the system

> to the best of my knowledge. I came up with

> about 59' of BB at 180deg. f.

>

> I have tried

> to work with my contractor but he won't even

> listen to his own guy(who's father is a heating

> professional) about this. He is relying on the

> rep's information solely. I just wanted to know

> if there was a possibility that there could be

> roughly a 14000btuh difference from one program

> to the other when it is for the same room. I

> have used calculators that I have found on the

> net and also information from other heating guys.

> I by nomeans want to start an argument about this

> or to sound like I am a professional. I am just

> frustrated and am looking for some

> answers.

>

> Thanks again for any input on

> this.

>

> Ray

Mike T., Swampeast MO

Is That Room on Its Own Zone?

Definitely believe that there shouldn't be any other B/B in its loop and that it should have its own thermostat.

A room like that picks up a lot of heat during the day and then starts loosing a lot at night. If on the same zone with other spaces, there WILL be problems.

A possibility for some of the calculation difference. With a wall of glass, some will compute BOTH an outside wall (the entire area) AND the glass. Some heat loss programs [might] automatically correct for this error, others may not. You should subtract the glass area from the wall area when computing loss.

Jed_2

Or, as exactly

in this case: (20 x 25)/15 = 33' standard baseboard. This is a "quick sizing formula" I've heard people ("the REP") use to size baseboard sytems. It's exactly what this rep came up with. Huh!? I've compared this quick calc to actual house plans with HE2 calcs (actually, I used either 17 or 20 as the divisor for a new, well insulated new house), and been pretty close. BUT, I would NEVER use that quick formula with a cathedral ceiling, one wall having 75% glass. Absurd!!

Frank,could this so called "Rep" supply you with the actual heat loss spread sheet? I'd demand it.

Jed

Mike T., Swampeast MO

Have you carefully inspected the ceiling in that space? Cathedral ceiling are notoriously difficult to insulate properly without special measures.

Have you verified that the insulation was installed in the type, manner and thickness used for the heat loss calculations? Don't forget that the code-required ventilation frequently takes some of the space that some might assume to be filled with insulation. Particulary if fiberglass insulation is used and there's good ventilation at the rear, the effectiveness of that insulation is GREATLY reduced by the air moving over and through it.

Lots of recessed lights? If so, I sure hope they were properly installed in SEALED and INSULATED "boxes". If not, they're extremely effective "chimneys" to the ventilation space at the rear of the insulation. Such only further increases air movement and further reduces the effectiveness of the insulation. Even if properly installed, the recessed lights become areas with relatively little insulation. A veru few don't matter too much, but if a lot--watch out! I've seen 30 or 40 in similar spaces.

Rigid insulation is a pain to install well, but it's HIGHLY desirable in a roof/ceiling combined construction.

STEVE N

Mike

Mike you may have hit the nail on the head. About 5 years ago I had the same situation. It was a radiant job and the customers were complaining about poor heating in the family room. Same deal 20ft high cathedral ceiling with knotty pine finish. They also had a fireplace. I kept telling them there was a construction problem. The fireplace was like a wind tunnel as well. I took my heatloss calc with me and even explained it. Things were starting to get heated between the owners and myself. I bought one of those lazer beam thermometers. Just point and shoot. After 5 minutes on my last trip there it was clear. 30 degree air coming out of the peak of the ceiling precipitating down. This also caused the wind tunnel effect at the fireplace. He tore down the boards at the peak and basically it was uninsulated.... the ridge vent was letting air in. He fixed it... no more problems. Remember... things always as they seem. Its not always the heating guys fault.
Hope this helps

Steve

Ted_9

Steve

I love a story with a happy ending.

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John Cockerill

no heat??

You can always add radiation. Do the rads in the room heat at all? If the boiler water is set too high the circulator runs less and the warm water may not be getting to that end room. Try lowering the aquastat to 150 and see if it helps. This increase your circulation and get the warm water to the end of the system with longer circulation. You can automate this process by measuring actual Termostat demand over time and adjusting the boiler water temps according to variance from ideal demand ratio. You will be toasty warm and save a bundle on lower water temps. Got ask? Is the thermostat in a good representatvie place??? may need to move it further away from the burner.

John Cockerill Exquisite Heat
www.Exqheat.com

Ken_8

Be careful...

Lowering the boiler aquastat setting will make things worse - not better.

With a wall of glass, I doubt more radiation can be added. The nature of the existing baseboard may need to be changed out to higher output type.

Thermostat location is not the issue. We can be assured the owner cranked the heat up to the highest setting and was still cold.

Pipe size and circulator dynamics may be at play here; but I wouldn't hold my breath on that one either.

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Steve_35

You're talking 14KBTUH difference in one room, right?

You don't really give enough info to come up with an accurate HL but assuming there's an unheated basement underneath, 3 exterior walls (2-20' and 1-25') with about 160sq ft of double pane low e glass total, 8' wall at the eaves and 20' wall opposite, average (simplified) infiltration, R-19 wall, R-38 ceiling and a deltaT of 80º I came up with 27,000BTUH loss.

If I change the infiltration to tight and the windows to the best possible standard rating I get 22,000BTUH loss.

Ask the heating rep for the data sheets.

BTW, something is up with the ceiling pitch. 12/12 pitch means it drops 20' in a 20' run so if the ceiling is 20' high at the high end it's on the floor at the other end.

Ultimately, it looks like you're going to need more emitter. BTW, don't use my numbers I did it just to get a feel. You need to look at the house as a whole particulraly with regards to infiltration.

GW

when I do a job

I'll state on the agreement what "air change per hour" I'm designing the system for, and of course insulation which is a little more obvious. So, if the place doesn't heat or cool when I'm done, I'll check the infiltration and see if it's my fault or the builder's fault (thankfully I haven't has to do it yet!)

Find a guy with a blower door (I have one). If the room is too leaky (you'd be mistaken if you think it's TIGHT just because it's new construction), the heat will find its way out. It has to; it's a law of physics.

I deduce that the plumber doesn't know anything about hydronics (many plumbers don't) and needs the rep for that reason. If the rep did a poor job, it's still the plumbers name on the job. Ask him who his insurance company is! Maybe that will get him to respond.

I totally agree with many comments here; you got some good free advice!

What state are you in? I'll see if I can find you a blower door guy.

Gary Wilson, Owner
Wilson Services, Inc.
Easthampton, MA
413-527-3317
gary@wilsonph.com
www.wilsonph.com

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leo g_13

It may be wise

to install commercial grade BB in that room, as some of them can put out up to 900 BTU/H per foot.

Leo G

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Mijola

Not enough heat

Frank,

Is the room in question on it's own zone? If not, what else is on that zone for that room and where is the thermostat for the zone located?

If it is a separate zone from the rest of the home, does it have it's own circulator or is it on a zone valve off of a circulator serving other zones?

Regards,

Ed

frank_31

WOW! alot of responses. sorry for the delay in getting back to this. been sick with the flu. The great room(problem room) is not on it's own zone. It shares the same zone as the kitchen and dining room. The thermostat is located in the hallway just between the greatroom and the large(12' wide) walkway between the kitchen/dining room.

I tested the system over the weekend according to how the plumber wanted to test it. I turned up the thermostats throughout the house to 80 on friday night at 6pm(outside low temp overnight was 32) and as of saturday at 7:15am there was only one room close to 80 and it was an upstairs bedroom, it was 76. The greatroom was at 70. The house did not heatup to 80 until monday afternoon when i just decided to turn everything back down and there were 2 zones(upstairs bedrooms) at 80 and the greatroom was at 78.

The contractor stated monday that he was bringing in a third party(neutral?) heating rep and have him evaluate the situation. So I'll post his findings. Oh ya by the way I do have the heatloss calculations from the original rep. if anyone is interested, plus the dimensions for my house.

Thanks

GW

heat loss

Even with a heat loss, it still doesn't mean anything; I had a supplier size a house for heat and AC a couple of years ago. He came up 5 tons. I thought it was too much, so I did it myself and came up with 3.5 (two systems). The house cools just fine. There's way too much room for input (human) errors.

Gary

Constantin

... and it only gets more complicated...

ACCA has released version 8 of their guidelines, with even more granularity in their results, etc. In theory, any two programs will produce the same results given the same inputs... yet, even armed with that data, all sorts of funny business ensues.

For example, IIRC, HVAC-Calc's author, Don Sleeth, advocates adding a safety factor of 25% to the the heat requirement results while sizing the AC side to the specs of his program. I believe two things are at work here:

• Undersizing a heating system will lead to call-backs. Adding a "safety factor" is insurance in case you don't know how to enter the data. Besides, the customer is paying for the fuel.
• Oversizing an AC system is pretty much as uncomfortable as not having one. An undersized system will always be able to take advantage of thermal flywheel effects and besides, unless it is grossly undersized, this issue will only surface on the hottest of days.

Then I look at the results from people who actually instrument homes like BuildingScience's work out in the midwest that showed how properly-built homes that had AC systems intentionally undersized by 20% had better comfort, lower cost, etc. than the homes where the AC system was sized to spec. Granted, this was a first year performance, when the coils and the ductwork are clean. Yet, with the proper maintenance and filter schedule, I'd like to think that one can live a bit closer to the edge.

Mike T., Swampeast MO

Undersized A/C

Did that last year in a rental. Good results with high comfort, low humidity and low operation cost, BUT there is a problem. In this very warm, humid climate significant daytime setback (or is that set-up) results in very poor comfort. Despite an "intelligent" setback thermostat, 3°-4° is the max the renter found for decent comfort when he comes home from work at about 4:30 p.m.

Constantin

Granted...

... if it's going to be setback significantly during the day, then you're going to need some added "oompf" to get the place cool quickly. This is no different from radiant floor constant circulation systems vs. oversized hot air systems. Since the structure is likely to be occupied 100% of the time, I doubt that the lack of setback capacity will affect us much.

My quandary centers around the 2nd floor system, where I'm either over by 6000BTUs or under by 3000 BTUS, depending on whether I chose a 2 ton or a 3 ton system to do the job. I could right-size using a 2.5 ton unit (which would be right on the money as far as the calculated heat gain is concerned) but it would be a different line of condensers than the one I was originally interested in.

Plus, we have relatively low humidity, there are trees that shade, fewer people per room than the worst case scenario I planned for, etc. Hence my inclination to undersize by 10%, giving that 2-speed compressor lots of runtime and taking advantage of the thermal flywheel effect.

Constantin

Mr. Carey,

Ed,

Please, if you're going to use a fake e-mail address in your posts, please don't subscribe to thread update notification. Otherwise, the Walls server program sends me a nastygram every time it can't reach you.

Thanks!

Mike T., Swampeast MO

This is probably the "swampeast" mentality talking, but in multi-story homes around here the best results I've seen/felt are when the ground floor is intentionally undersized and the 2nd floor oversized by nearly the same amount. You probably have two open staircases and I've yet to see a heat gain program that "understands" that warm air rises and cool air falls through the stairwells.

I've been in two different two-story old houses around here that kept their radiators and A/C is installed in the attic only. A huge amount of air is "dumped" into the most open end of the stairwell(s) with a large return opposite (near the head). As long as the downstairs is quite open, the comfort level is suprisingly high at minimum installation cost. If no rear stairs leading to the kitchen, it's best to get at least one supply and return down to the kitchen.

Constantin

That's a very good point.

Don Sleeth @ HVAC-Calc could never answer my question re: the open stairwell effect satisfactorily and your insight makes a lot sense. I guess I'll go with the 3-ton unit for the attic and call it a day. With the condenser modulating its output, hopefully the system will behave itself.

Mike T., Swampeast MO

Since you seem to enjoy efficiency and have a good budget, here's something to consider. Would LOVE to hear from anyone who has actually used the thing.

Rawal (www.rawal.com) valves for the A/C units.

They supposedly turn a standard condensing unit into one that effectively modulates (via modulating bypass controlled via the evaporator) without sacrificing energy efficiency. Everything runs nearly continually and when heat gain is low, it supposedly turns the evap into a dehumidifier removing mainly? only? latent heat.

Constantin

It's certainly interesting...

... particularly for those with basic single-speed condensing units. With all the lockouts that the HSX19 has, I'm afraid that retrofitting such a device will make the control logic light up like a pinball machine.

Furthermore, given what a low percentage of the load latent heat is around here (less than 10%), I'm frankly afraid of what'll happen to the wood in the house if the moisture levels keep dropping because the AC is running.

I think I'll stick to the OEM stuff for now...

KBP&H

return temp & boiler

have your contractor ( or someone else) install a return temp thermometer on the system or find some way of checking the return temp to the boiler,, if that zone is more than 20* less than feed or about 170, thee's toooo much on the zone,, sometimes i've seen systems that there's tooooo much temp drop or more load than the boiler can handle,, the boiler could end up in a situation where it can't raise the water temp ( with everything going) and it will end up stalemated - sit there and run but not do anything. it's hard for anyone here tofigure it out exactly, but were all trying to give you different insights,, i know this isn't up to you,, so tell your contractor about all of US.

Jed_2

900???

Gee, Leo, I can get commercial baseboard radiation that'll put out 1300-1800 btu/ft.

Mijola

E-mail address

Constantin,

Sorry for any problems with that e-mail address. I took the check out of the update box on my post.

The thread will not take the post without that field filled in. As you see I listed it, "nospam@nospam.com". I will give you three guesses why I post that, instead of my actual e-mail address.

If you need my actual address, please let me know. I will post in the open with the proper keys to assemble it. I just do that in an attempt to fool the spam bots.

Regards,

Edward A.(Ed) Carey


E.A. Carey HVAC

Mijola

E-mail address

Constantin,

Sorry for any problems with that e-mail address. I took the check out of the update box on my post.

The thread will not take the post without that field filled in. As you see I listed it, "nospam@nospam.com". I will give you three guesses why I post that, instead of my actual e-mail address.

If you need my actual address, please let me know. I will post in the open with the proper keys to assemble it. I just do that in an attempt to fool the spam bots.

Regards,

Edward A.(Ed) Carey
E.A. Carey HVAC

Mijola

E-mail address

Constantin,

Sorry for any problems with that e-mail address. I took the check out of the update box on my post.

The thread will not take the post without that field filled in. As you see I listed it, "nospam@nospam.com". I will give you three guesses why I post that, instead of my actual e-mail address.

If you need my actual address, please let me know. I will post in the open with the proper keys to assemble it. I just do that in an attempt to fool the spam bots.

Regards,

Edward A.(Ed) Carey
E.A. Carey HVAC

Mijola

E-mail address

Constantin,

Sorry for any problems with that e-mail address. I took the check out of the update box on my post.

The thread will not take the post without that field filled in. As you see I listed it, "nospam@nospam.com". I will give you three guesses why I post that, instead of my actual e-mail address.

If you need my actual address, please let me know. I will post in the open with the proper keys to assemble it. I just do that in an attempt to fool the spam bots.

Regards,

Edward A.(Ed) Carey
E.A. Carey HVAC

Mijola

E-mail address

Constantin,

Sorry for any problems with that e-mail address. I took the check out of the update box on my post.

The thread will not take the post without that field filled in. As you see I listed it, "nospam@nospam.com". I will give you three guesses why I post that, instead of my actual e-mail address.

If you need my actual address, please let me know. I will post in the open with the proper keys to assemble it. I just do that in an attempt to fool the spam bots.

Regards,

Edward A.(Ed) Carey
E.A. Carey HVAC

Mijola

Not enough heat.

Frank,

When you turn up that thermostat for the subject zone, does the water run into the great room first, or into one of the other rooms first?

Per my other question posts, is that zone on it's own pump or a zone valve?

Please describe the general construction characteristics of the other rooms on that same zone in comparison to the great room, ceiling height, window size, room orientation to N, S, E, W, etc.

You said that the great room eventually got to 78 degrees. What was the temp of the DR & Kit, when the great room finally got that warm?

Regards,

Ed Carey

WPH2205

Frank, it sounds to me like you may have more than one problem. First off, determine what size baseboard you have. If it's 3/4" copper, you can only run 67 feet of element on that loop before you run out of heat.(3/4" copper flowing 4GPM, 1GPM=10,000btu, 4GPM=40,000btu, 40,000btu divided by 600btu/ft. of baseboard=67feet). Also, I don't know where you're located but here in northeast PA. we figure our design temp. difference at 80 degrees.(Enough heat to maintain 70 degrees on a 10 below 0 day).

leo g_13

I was

thinking about for home use. I just find the really high output BB's to be quite ugly in home use. That's all.

Leo G

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Constantin

Hi Ed,

I have no issues with you posting under a fake e-mail address to avoid the spam bots. That's perfectly fine.

All I'm asking for is that if you check off the thread update notification that you have a valid e-mail for the Invision system to send a thread notification to. Otherwise, every person with a valid e-mail address that contributes to this thread gets a notification from the Wall every time they post that the Wall could not send the article to you because of the bad e-mail address. Cheers!

Mijola

Fake e-mail

Constantin,

Thanks for the response. Also, thanks for the heads up on that issue of return e-mail address. I never gave it a thought. I understand now and it won't happen again.

Regards,

Ed