Cheese .. design question..Boilerpro

Boilerpro

Your thread got buried and I didn't see it until I checked E-mail. The answer to your question is a definite yes. In newer, better insulated homes infiltration is typically a much higher percentage of the total heat load, often 50%, since the conductive heat loss through walls and ceilings is nearly eliminated. It may be a lower load, but the percentage is higher. For this reason, I would consider it even more important to take into account exposure, lower/upper level etc. Insulation and most housewraps don't have as great an effect on infiltration as one would expect. Most housewraps are perforated, allowing the wall to breath but also allowing increased infiltration ( Tyvek is the one exception I can think of). No matter what the age and construction, when looking at just the stack effect infiltration, cold air will always enter the lowest portion of the structure and heated air will exit the top, therefore, you will always need proprtionally more heat on a lower level than an upper. Really good question!

Boilerpro

Mike Kraft

Thanks

There must be an energy flowing....aaaaaaahhhhhhhhhhmmmmmmmm!I just clicked my way in here:)Some that I have spoken with in the past and in the present have defaulted infiltration to one ACH for the home.Not based on what a room x room exposure would be.I have been "fitting" an ACH for each room.Sinc eusing the new software (Slan Fin) I am finding that my loads are higher than when I did them long hand.Using the same method.Obviously the long hand I used was falling short at times but not significant enough to lay awake @ night:)

This ACH has always been my brick wall.......one of many:)I understand that forced air and HWBB crates convective currents.......I get that.I also get that RFH doesnt........it heats objects not air.Ergo no air movement.BUT...........infiltration is infiltration.Construction is what it is.Regardless of the heat source.......right?So if this is correct why do we or most lower the infiltration rates for RFH to .5/hr reardless of exposures?I try to see but cant open the peepers all the way.

thanks boilerpro

Boilerpro

I think your eyes are beginning to open

You hit the nail on the head when you mentioned convective air currents, just didn't realize it. Convective air currents increase infiltration. As that warmed air rises to the ceiling, (or up the staircase to the second floor) it is decreasing the pressure near the floor and increasing it at the ceiling, and you begin drawing in outdoor air near the floor (infiltration) as its leaks out at the ceiling. This air movement also disturbs the insulating layer of air next to walls and ceilings, lowering their R-value. If you add the pressure differential of a furnace fan, you are likely to create even greater pressure differentials in a home, especially when you look at how leaky even good ductwork is. A structure and a heating system work together to either increase or decrease the efficiency of the overall system. In my opinion, this is why many well maintained, but poorly insulated old homes with 80% boilers and standing radiation are less expensive to heat than new well insulated homes with 92% AFUE hot air furnaces.

Boilerpro

Mike Kraft

Getting a visual

and am definitely grasping the why part much better.So it could be assumed that in designing a heat loss and simply allowing one ACH factor for the dwelling uis a bad practice.Does this hold water for a RF design also?Or is this a much "safer" scenerio for allowing one factor regardless of the exposed panels to rooms.

One application I have been doing for some years now is to include a small length of HWBB or panel rad on these Great Room zones up on the walkways or staircases that overlook these rooms.My "theroy" is that when that particylar zone(1st floor) zone bangs on some heat will be circulating at the level above to try to combat the air flow.

cheese

Boilerpro

Trying to talk to two people at once

Got the big Dan on another thread. Never thought of it that way, but I would expect it is safer to use one infiltration number for the whole structure with radiant, but you still have the potential for wind loading... lots of cold air coming in the windward side and increased heat loads and that warm air from those rooms helping the rooms on the leeward side keep warm where it is leaking out. I've thought the same thing about trying to catch some of the cooler air coming off the walls and ceilings with a baseboard placed up high. I'm sure youv'e been at this longer than I, does it seem to work? I imagine when combining quick cooling baseboard with slow cooling radiant, you'd want constant circulation between the two to keep everything heating evenly or reset water temps.

Boilerpro

John T_2

> You hit the nail on the head when you mentioned

> convective air currents, just didn't realize it.

> Convective air currents increase infiltration.

> As that warmed air rises to the ceiling, (or up

> the staircase to the second floor) it is

> decreasing the pressure near the floor and

> increasing it at the ceiling, and you begin

> drawing in outdoor air near the floor

> (infiltration) as its leaks out at the ceiling.

> This air movement also disturbs the insulating

> layer of air next to walls and ceilings, lowering

> their R-value. If you add the pressure

> differential of a furnace fan, you are likely to

> create even greater pressure differentials in a

> home, especially when you look at how leaky even

> good ductwork is. A structure and a heating

> system work together to either increase or

> decrease the efficiency of the overall system.

> In my opinion, this is why many well maintained,

> but poorly insulated old homes with 80% boilers

> and standing radiation are less expensive to heat

> than new well insulated homes with 92% AFUE hot

> air furnaces.

>

> Boilerpro

eleft(retired)

design

Sooo ......

..after the constriction is complete with all the defects you guys are eluding to, what does the engineering mind do to correct or overcome the problems?

al

PJO

Convection in open areas...wind side issues...

Cheese and Boilerpro,

This is a great discussion, and I have wondered about this myself...although I don't do any designs. I agree that the convection issue is greatly reduced for RFH vs. HWBB, and see proof of it it my home.

I put HWBB upstairs and RFH on the first floor and garage slab. I have an open area where my stairs go to the second floor, and there is hardly any air movement there compared to my last home (all HWBB). When the HWBB is coming on from setback for the morning crowd, I can feel more (convective) air currents flowing down the stairs...I often sit on the landing with a cup of java and the dog for a few minutes and notice this in case you're wondering :-)

I would think if you purposely put a convector or radiator there (on the first floor under the open area), it would tend to increase the convective current (convector more, radiator less)...sending warm air upstairs and cool air downstairs. Does this make sense?

As far as the infiltration goes, I have a small opening in my door to the gaarge between the door bottom and the threshold (it's on my "honey-do" list). I notice that when I get a good fire going in my fireplace and do not open a near window a bit (for intake air) that this opening has some serious air flow. My garage is pretty warm, so it doesn't affect the house temp too much - plus the air is flowing across a warm floor - but it definitely is the intake for the fireplace.

When we have a stiff breeze - usually western - and the garage doors are open (western exposure) there is a very good flow through this opening as well...definitely proof of Dave's statement about "windside" affect. The mudroom has a vinyl floor and the radiant does well there, so (again) it doesn't adversly affect things...but I could see this being a problem in lots of other situations.

The house is fairly tight...never had a blower door test, but all openings where sealed during construction 4 1/2 years ago, and the house is Tyvek-wrapped. I also took extensive time to seal openings around windows, outlets, etc. I believe this contributes to the heatloss calc. given to me being too high...it was Manual J...does this make sense?

Can I say that this issue is very important when designing the heating for an "un-tight" house in the open with convectors, and not as important for a tight house with a solid row of dense pine trees along the prevailing wind side, and radiant floor heat? I guess the question is; What about everything in between?

Great Topic! Take Care, PJO

j_4

infiltration

this is what Trane Trace700 load calc software uses for infiltration

Mike Kraft

These are my concerns

I am sizing equipment and emitters.I design sell install comfort in trusting clientals homes.I put much effort to install all of the above with a very large amount of confidence and clear conscience.After all, as mentioned in the arborist post I have passion and knowledge of what I do.I convey that to my clients.

But this infiltration gig is interpreted through many mouths and schools of thought.As seen by the couple of posts.I have used the "Slant/Fin Fitters Guide" for years.It has never let me down.......ever.It is a well laid schedule of how to design room x room.I have recieved the software and love its ease also.My stumbling block has been through all of it the ACH.

I have talked to other designers and very suprisingly recieved answers that lead me to relize that this ACH # is seat of the pants at times.I tend to agree with boilerpro and the SF guide and be conservative.I am not familar with the Trane method or Manual J.But looking at the scenerios that j left it appears that Trane allows one default for the construction method.This choice is not specific or very descriptive.In contrast the S/F guide is.This choice as in all methods is left to the designer.

My point?Well,I'm not sure anymore:)I guess there are many ways to size a dwelling.ACH is a big #.There are conflicting ideas and methods.I tend to find my comfort zone and walk the same direction as the rest.But sometimes I gotta walk the other way and ask questions while I'm getting there.Even if I find myself back in the order.

cheese

Mike Kraft

Heres a look at Slant/Fins

Defaults

cheese

[Deleted User]

Those are...

the old I=B=R numbers, and they are conservative. Don't forget, you have a LOT of internal mass that helps offset the infiltration loads over a period of time.

Nothing is pure, including heat loss/gain factors. They are simply a SWAG factor that get us "in the ball park" as it pertains to a dwellings heat loss.

For those who have not been exposed to SWAG, it stands for Scientific Wild A$$ Guess, it's an engineering term:-)

All in all, there's a lot more diversity in loading than we take into consideration. There's internal gains that we don't account for, internal mass that we don't account for, and infiltration factors that are estimated a lot higher than real world conditions. But you HAVE to start somewhere, and that somewhere is a heat loss calculation.

If you don't do one, you're just guessing.

Stick with what you're comfortable with. If it ain't broke, why fix it?

ME

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Mike Kraft

guess I.......

am a bit relentless:)

cheese

Cosmo

Don't see it as a fault

We are all here to learn, and the best way is to hammer at a topic until it makes sense..... sometimes this takes a while but it is always worth it.
I have been using the new Wirsbo Advanced Design suite program for radiant ,and it too only has as the infiltration factor a selection between good, average , and poor grades of construction. I also use the slantfin software for convection heat loads and you are right about that, it gives you a selection between different outside wall construction materials.


Casmo
Dependable P.H.C. Inc.

ScottMP

Don't ever stop Cheese

This had been a great post.

I use a program called E-Z heatloss, made by Thomas and ****. in MI.

It is e-z, and my only adjustment is to change the infiltration with one based on volume and one air change per hour. I just got the SL Explorer, Thanks Noel, and when I get a chance see how the two line up.

Scott

Scott

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Mike Kraft

Patty me boy

I relate my brother from another mother.I sit at the bottom of my stairs (and still dont have RFH,barefootn shoemaker kids) and feel the breeze.Also coffee in hand but my bear dog is missing he left us 1 1/2 years ago:(.........but the breeze be there.And it is a breeze my friend.

The stairs have an 8' slider in front of them.And @ the top os the stairs in the ceiling is a scuttle hole for the attic.So this is a hair raising breeze:) a damn noreaster!

This is how I thought up the idea of adding heat to the second floor landing.This heat would run with the first floor stat.Theory is it will preheat the "high air":) I have done it in several homes with huge ceilings and all the glitz.I havent lived it and dont know if it helps but it sure cant hurt eh?

I was wondering what the temp difference is between 1st and second floor.And whats the lay of the land?Both ceilings 8'?Its funny to see them currents in action.

attached is Bear dog.He was a large part of the families lives and is sorely missed!

cheese

Gary Fereday

Garage & house opening ?

I hope there is a 2 foot or more raise between the Garage and the house. Gasoline leaking in the garage could be ignited by the fire place and BOOM! Just a safety thought bigugh

Boilerpro

Ever gone back to a job...

On a design day (following several others) first thing in the morning (no solar gains and internal gains) to see how much the boiler is working? Not too often is it working at 100% minus the pick up load. I agree with some of the ohter posts that most of the current heat loss calcs are very conservative. Some one also mentioned thermal mass. When working with masonry structure, especially those with lots of interior concrete (flexicore, etc.), I usually keep my heating capacity down somewhat than in frame struture. Grew up in a 12 brick home in Chicago with a huge Maple shading to the west. Usually took 2 to 3 days of really hot weather before we would need to turn on the A/C. Figure same thing happens in the winter, all that thermal mass moderates rapid temperature changes outdoors. Also, when calculating loads in masonry structures, the structure becomes thermally coupled to the ground. The heat in the ground is conducted up the walls moderating extreme outdoor cold. Heat loads on levels near ground level should be lower due to this effect. Haven't found any heat load calc that take into account the effect of mass and ground coupling. I was taught the CLTD method for cooling calcs in my classes which has factors for mass, solar gain, internal gains, and length of occupancy, but I've never seen this for heat loads. So yes I'd say some of this is still seat of the pants.... I'd say a little too much.

Boilerpro

PJO

Of dogs, brothers and (oh yeah) convection...

Cheese,

Sorry to hear about Bear...was he a Newfoundland? Tough to tell by the picture, but he looked beautiful. Looks like he loved that snow! My yellow Labrador left us two months ago, but we got another puppy this summer...knew he was gettin' near his time due to an aggressive cancer, so we decided to make it an easy transition for the kids. Not to get long-winded (it's the heritage...), but he never chewed anything except food, never got on furniture, only barked when he meant it, and NEVER even looked at a kid wrong. He put up with severe punishment from all three kids (he was born 9 months before our first), but he always was "rewarded" by sitting next to the high chair :-) Eleven and a half years of total dedication...even fought off a huge stray one time to protect our twoboys.

On to the heat...I have 9' ceilings downstairs, and 8' upstairs. The radiant first floor comes on at 5:00 from setback (people argue about constant circ/recovery/etc. but this works for me - it's staple-up w/ plates of course!). The second floor comes on at 6:30. They both are set at 70F, and the second floor (of course) reaches much faster. I am seriously considering adding two short lengths of Runtals to the first floor family room area...lots of windows, a french door, and cathedral ceiling make this the slowest recovery area. Management has the proposal and has not yet approved funding...I'm trying to "sneak-in" other improvements as well, but that's another story.

The lay of the land...as stated, the family room was the toughest challenge, and the stairs come down right between here and the kitchen. First floor all hardwood except a small study (management's office) of carpet and a border hardwood/carpet area for the family room. For these two carpeted areas I put nearly all soild plates and a bit more insulation, but on design days it's just short. This is also where the fireplace is, and I use it nearly every night of the season when I am home...another proposal to management is for a woodstove, but that is forever stuck in negotiations :-)

Cheese, I didn't realize you where putting the "extra" heat emitter upstairs where the opening is...I thought it was at the bottom of the area (downstairs). I wonder what difference it makes, if any. If you where slick, how about RFH on the landing? I'm sure HR has done that at least five or six times :-) Maybe even the whole set of stairs...that would be the ticket!

Enough of my rambling. Allman Bros..."Lord I was born a ramblin' man (not travelling either!)..."

Take Care, PJO (Former Scranton Brother)

PJO

Yes, bigugh...

that's about the difference in height, and thanks for the concern. I do not store any combustibles out there, but the cars are a concern. The fireplace is pretty far from the door to the garage, but I bet the gas fumes woudn't care!

I also don't have any combustable appliances except the boiler, which is direct vented. It still is a concern, though. I also keep a window cracked open in the garage until it gets real cold, but it's more for the "doggy" smell from her cage...this probably makes the air infiltration worse?

Another reason to fix it quick...thanks. PJO