Does this Load Calc sound correct- Sizing Question?

[shovel99]

Hi gents.

Do these load calculations look right.... and since I have a two story with two large stairwells allowing substantial heat rise/cool air descend... should I make any adjustment for that in sizing?

I have completed two load calculations using HVAC-Calc (Sleeth program) for my 1985 construction 2 story plus unheated basement. One for each system: main floor and unconditioned basement and 2nd floor.

Traditional 2 story, 1200 SF main floor + 70 SF of stairwell plus 300 SF of cantilevered sunroom with lots of glass, 2 skylights and cathedral ceiling= almost half the losses and gains on the 1st floor. Windows are double thermo pane. I assume R11 in the walls, measure 8 inches or R26 in the attic (2nd floor load).
Floors are all hardwood, no insulation above the basement. Basement is 2 sides completely below grade, one side is half below grade, and back wall is studs with r11 insulation but only 3/16 inch pseudo wood paneling. I assumed only 2 people... on the main floor. Should I include more... I have seen 2 persons per bedroom but ???? I have had up to 75 people in parties.... usually during heating period.. but what about a summer party? 50 people can double the AC load.


Design temp Atlanta GA winter 21 summer 95. Inside W 72 S 75

Don Sleeth, author, suggests doing load with basement as conditioned even though it isnt... to reflect significant losses? When I drop out the basement completely and change the floor to "over unheated basement" it drops about 6k BTU off the heat load. Don also suggests upsizing the heat by 20-25%, but that as much as any will be a function of what sizes are available. My 49k would be80% of 60k.

1st floor: 2770 SF (1500 main floor and 1200 basement) Total gain: 36k (3T), loss 49k.

2nd floor: 1626 SF (1200 plus 225 of bonus room over unheated garage, outside air on three sides with two gables... plus heated and cooled stairwell over ceiling/roof combo) .... 21k Air ... 28k furnace. These just seem a little low, especially air, which has the heat rising from downstairs through the two stairwells.

At any rate, I would greatly appreciate your thoughts if these sound right for a pretty standard builder grade 2 story traditional home.

Glad I learned of HVAC-TALK so that at least this time I could do or obtain a load calc and right size my equipment, unlike my experience in 2009 with no fewer than 3 contractors not even breathing a word about sizing other than to "match" what came out of a 1956 home that was built with no insulation at all.

Thanks in advance, Paul

[shovel99]

Bump to top. So no clarity from the experts?

Thanks, Paul

Hi gents.

Do these load calculations look right.... and since I have a two story with two large stairwells allowing substantial heat rise/cool air descend... should I make any adjustment for that in sizing?

I have completed two load calculations using HVAC-Calc (Sleeth program) for my 1985 construction 2 story plus unheated basement. One for each system: main floor and unconditioned basement and 2nd floor.

Traditional 2 story, 1200 SF main floor + 70 SF of stairwell plus 300 SF of cantilevered sunroom with lots of glass, 2 skylights and cathedral ceiling= almost half the losses and gains on the 1st floor. Windows are double thermo pane. I assume R11 in the walls, measure 8 inches or R26 in the attic (2nd floor load).
Floors are all hardwood, no insulation above the basement. Basement is 2 sides completely below grade, one side is half below grade, and back wall is studs with r11 insulation but only 3/16 inch pseudo wood paneling. I assumed only 2 people... on the main floor. Should I include more... I have seen 2 persons per bedroom but ???? I have had up to 75 people in parties.... usually during heating period.. but what about a summer party? 50 people can double the AC load.


Design temp Atlanta GA winter 21 summer 95. Inside W 72 S 75

Don Sleeth, author, suggests doing load with basement as conditioned even though it isnt... to reflect significant losses? When I drop out the basement completely and change the floor to "over unheated basement" it drops about 6k BTU off the heat load. Don also suggests upsizing the heat by 20-25%, but that as much as any will be a function of what sizes are available. My 49k would be80% of 60k.

1st floor: 2770 SF (1500 main floor and 1200 basement) Total gain: 36k (3T), loss 49k.

2nd floor: 1626 SF (1200 plus 225 of bonus room over unheated garage, outside air on three sides with two gables... plus heated and cooled stairwell over ceiling/roof combo) .... 21k Air ... 28k furnace. These just seem a little low, especially air, which has the heat rising from downstairs through the two stairwells.

At any rate, I would greatly appreciate your thoughts if these sound right for a pretty standard builder grade 2 story traditional home.

Glad I learned of HVAC-TALK so that at least this time I could do or obtain a load calc and right size my equipment, unlike my experience in 2009 with no fewer than 3 contractors not even breathing a word about sizing other than to "match" what came out of a 1956 home that was built with no insulation at all.

Thanks in advance, Paul

[jimj]

I assumed only 2 people... on the main floor. Should I include more... I have seen 2 persons per bedroom but ???? I have had up to 75 people in parties.... usually during heating period.. but what about a summer party? 50 people can double the AC load.

Number of bedrooms plus one is the correct people load. Don't be sizing for parties you have two times a year for a few hours!

[shovel99]

Number of bedrooms plus one is the correct people load. Don't be sizing for parties you have two times a year for a few hours!

Thanks Jim.

[dan sw fl]

___ VERY DIFFICULT to address even ONE of these,
... ... Five in combination: one better have experience and time
... ... to address the complexity.
1. Stairwell
2. 300 SF of cantilevered Sunroom with lots of glass,
3. 2 skylights
4. Cathedral ceiling
5. ROOM Above Garage

THIS CONFIGURATION SEEMS TO BE _FAR FROM A STANDARD BUILDER GRADE_ TWO STORY.

To give a REALISTIC estimate I would have to study real DETAILED plans, Specs and duct work
for about 5 hours to say if sizing and air distribution were adequate.

AND I am normally willing to give an approximation.
I really wonder about 21,000 BTU/Hr upstairs and air distribution.

Any summer party > 83'F and > 20 people and you will likely have to get additional temporary cooling.
_ Spot Cooler rental
OR stick to Spring, Fall or Winter parties.

http://www.harrisdiversifiedllc.com/...togallery.html

MOVINCOOL
http://www.americanspotcooling.com/a...ling,_Atlanta/

[shovel99]

Thanks Dan. You have explained why I am not getting other responses. Lots of moving parts. I will continue to check the 2nd floor calcs. Most immediate need is the system on the main floor 28/11 years old. Paul

___ VERY DIFFICULT to address even ONE of these,
... ... Five in combination: one better have experience and time
... ... to address the complexity.
1. Stairwell
2. 300 SF of cantilevered Sunroom with lots of glass,
3. 2 skylights
4. Cathedral ceiling
5. ROOM Above Garage

THIS CONFIGURATION SEEMS TO BE _FAR FROM A STANDARD BUILDER GRADE_ TWO STORY.

To give a REALISTIC estimate I would have to study real DETAILED plans, Specs and duct work
for about 5 hours to say if sizing and air distribution were adequate.

AND I am normally willing to give an approximation.
I really wonder about 21,000 BTU/Hr upstairs and air distribution.

Any summer party > 83'F and > 20 people and you will likely have to get additional temporary cooling.
_ Spot Cooler rental
OR stick to Spring, Fall or Winter parties.

http://www.harrisdiversifiedllc.com/...togallery.html

MOVINCOOL
http://www.americanspotcooling.com/a...ling,_Atlanta/