Below are some helpful hints when selecting Ceiling materials in Cool Calc:
Attic Ventilation - If the attic contains ridge vents, eaves, soffits, or fascias, and is vented according to the US Federal Housing Authority guidelines select “FHA Vented”
Attic Fans - Often times, after a hot day, the temperature inside of a home can be higher than the temperature outside of the home. Attic fans (or whole house fans) exhaust hot air through vents in the attic, causing a negative pressure in the home, which draws in cool air from the outside (saving money on air-conditioning). The presence of an attic fan can be identified by a grille in the ceiling of a central hallway or outside gable vents on the home.
Radiant Barrier – A radiant barrier is a foil-like material that reflects heat. This is typically used only in the south.
Ceiling Insulation - If there is an attic, ceiling insulation can either be applied to the attic floor or the along the roof rafters. If the insulation is applied to the roof rafters, the attic is referred to as an "Encapsulated Attic". If "Encapsulated Attic" is selected, Cool Calc will automatically calculated the temperature difference between the attic and living space based on ACCA tables.
If the insulation is applied to the insulation floor the user can either have Cool Calc automatically calculate the most likely R-value, or manually enter the r-value (if known).
If you have access to the attic, the R-value of the insulation can easily be determined. Fiberglass insulation will typically have the R-value printed on the paper backing. Attics, may also have Cellulose Insulation (typically made from recycled paper) blown in on the attic floor. Cellulose Insulation has an R-value of about 3.8 per inch. You can use a ruler to measure the insulation depth in the attic and multiply it by 3.8. For example, if the insulation depth is 12 inches the R-value is most likely around 45 (3.8 * 12 = 45.6)
Some rooms have cathedral ceilings. Cathedral ceilings or ceilings with exposed beams typically have lower R-values since there is a smaller cavity to fit the insulation into. For example, a standard 2x10 roof joist would be able to fit about 9.5 inches on insulation.
How bout a duplex or apartment with another unit over it. How to indicate conditioned space over the lower unit's ceiling?
I just asked the same question . . . I don't think there guy even thought about it . . . .
Can we please get an answer on this? I only work on multi-family dwelling units for HVAC design. I would love to use cool calc and it seems it's just a small adjustment to make it so the floor above is not a roof but another conditioned space.
You can handle this scenario two different ways. If you are using the map trace feature, you must trace the multi-family unit above the unit you are calculating the load for and the program will automatically omit the ceiling load. Then in the HVAC Systems section you can use the "Rooms in Systems" link to omit the multi-family unit above from the system. Alternatively, you can use the "Text Editor" option and just manually delete the ceiling above the room you add.
in the picture above what considered wall space or roof space. if insulation is sprayed to the bottom of the roof deck?
If insulation is sprayed on bottom of roof deck, and the space under the roof deck is not living space, then it's considered a ceiling under an encapsulated attic. If the space under the roof deck is living space, then it's considered a ceiling below roof joists.
one other question what would the wall height be in the image above for the attic area since there is no wall just ceiling?
If you choose the "encapsulated attic" option, CoolCalc doesn't let you specify the level of insulation. The article below implies it assumes R19. My project has R49 closed cell spray foam on the attic rafters. Is there a way to adjust the assumptions?
https://coolcalc.zendesk.com/hc/en-us/community/posts/8461995288211-Insulation
The Manual J book uses predefined temperature differences between an encapsulated attic and the floor below it. Depending on the area of the country there is a 4-9 degree temperature difference between the attic and living space in the winter and 3-5 degrees in the summer. We do not have an option to manually enter the temperature difference for higher insulation values at this time. R49, may have a slightly lower temperature difference, but I don't think it will make a material impact.
So if you have a ceiling under roof joist with spray foam insulation, what insulation choice do you choose? The options shown are blanket or loose fill?
Hi Brandon, you would still choose blanket or fill but try and match the r-value. Closed cell spray foam is roughly R-7 per inch while open cell is roughly R-3.8 per inch. Most ceilings are either open cell or a combination of closed and open cell since it is not recommended to apply closed cell spray foam over 3 inches for curing purposes.