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project development & documentation
21

I have a question regarding the uses of baseboards and crowns in a single-family house.

  • I know we need baseboards and crowns for a number of reasons, but do different construction systems will determine whether or not we need baseboards and crowns? I do not see them often in public buildings (office, museum, restaurant, etc.) but usually see them in private buildings (single-family house etc.).

  • What if we want to have a house without having baseboards and crowns and to make the house modern and clean like the ones designed by Richard Meier? How can we do that and what are the design implications?

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These are great questions!! @coachbryanhadley think you could help @arch123 with these questions?

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Greetings @Arch123,

Baseboard trim and crown molding are strictly applied for aesthetic reasons. They are not dictated by construction type, occupancy, use or any other such criteria.

You can think of baseboard trim and crown molding as band-aids. They are absolutely not necessary but are commonly applied to cover imprecision where other finish materials meet, such as at the intersections of wall and floor, wall and ceiling, and around windows and doors. This allows the contractor a bit of wiggle room to work more quickly because the trims will cover any small gaps or jagged edges, and where materials may need to be allowed to move independently. These trims can be a strategic advantage for an architect who is trying to utilize control joints to mitigate the impacts of thermal expansion / contraction, but doesn’t want them to be seen.

If you want to design your home to have a clean, simple, linear aesthetic, by all means, go ahead. You’ll just want to make sure that you’re balancing cost and performance trade-offs while you dial in the aesthetics you want. It all comes down to the details. You might choose materials that are more forgiving and which allow for cleaner joint conditions, and stay away from ones that are more difficult for the contractor to achieve the desired effects.

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24

I need help on how to calculate the U-Value of a wall assembly in elevation, the parameter given are the wall U-Value and and the window(s) U-Values on that particular elevation.
I also need help on how to calculate the U-Value of a roof assembly, not sure what to do with the overhang.

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25

Hi @josemo let’s see if we can get those questions clarified. @cat.heard9 do you mind helping with these calculations?

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26

Hey @josemo, let me see if I can help bring clarity to your question.

To calculate the U-value of a wall in elevation, you’ll need the dimensions of the wall, dimensions of any penetrations (doors and windows) in the wall, and the R or U values for the wall assembly and door/windows.

Let’s start with the formula we’ll need to accomplish this: U-value = 1 / (sum of all R-values).

Not all assemblies will cover the same amount of space on the building, however, so we’ll need to multiply the various assemblies based on the percentage of area on the elevation. For example, if we have a 12’ x 40’ wall, with a 3’ x 7’ door, and two 2’ x 3’ windows, we’d calculate the area as follows:

  • Total elevation area = 12’ x 40’ = 480 SF
  • Total area of the door = 3’ x 7’ = 21 SF
  • Total area of windows = 2 (2’ x 3’) = 12 SF
  • Total area of the wall assembly = elevation area - penetrations = 480 SF - 21 SF - 12 SF = 447 SF

Total percentage of area of each element:

  • (Door area / total elevation area) x 100 = (21 SF / 480 SF) x 100 = 4.375%
  • (window area / total elevation area) x 100 = (12 SF / 480 SF) x 100 = 2.5%
  • (wall assembly / total elevation area) x 100 = (447 SF / 480 SF) x 100 = 93.125%

To double check your math, the total percentages should equal 100%. 4.375% + 2.5% + 93.125% = 100%. As a note, if you come across a question that gives you uneven numbers, or numbers with many trailing decimals, check the question verbiage for how many decimals to round to, and use this as a guide for rounding numbers in your calculations.

Next, if the question doesn’t give R values for each element, calculate the R-values for each assembly with information in the question text. Multiply the R-values of the assemblies by the percentage of the elevation to find their effective insulating value as part of the elevation. For example, if we were given the wall assembly = R-12, the door = R-6, and the windows = R-8, our calculations would be as follows:

  • R-value of door per elevation = 6 x 0.04375 = 0.2625
  • R-value of windows per elevation = 8 x 0.025 = 0.2
  • R-value of wall assembly per elevation = 12 x 0.93125 = 11.175
    Add the R-values together to determine the sum. 0.2625 + 0.2 + 11.175 = 11.6375.

To determine the U-value of the assembly, we return to the original formula of U = 1 / sum of R-values. U = 1 / 11.6375. U = 0.08592911, or approximately, 0.086.

Does that help answer your question?

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27

As for the roof assembly, can you expand on what you mean by the overhang? Is the question whether or not it should be included in the calculations pertaining to the overall U-value of the roof?

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Does wood veneer that is used to finish a wall fall under division 9 or division 6?

Same question also, but for wood panels used to finish a wall?

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29

Hi @Shikha ,

Great question! Typically, I would assume wood products including panels and veneer will fall under division 6 - Wood & Plastics by default. However, it can depend on how exactly it’s used. Any applied finish for wood products would fall under division 9.

In addition, some manufacturer’s might list their proprietary veneer systems under Division 10: specialties.

This PDF of ‘Architectural Woodwork Standards’ has some more information about specifying wood products if you’re interested in learning more.

Hope this helps!
-Darion

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Hi Darion!

So what you’re describing in your example is similar to adding a stain to a piece of wood or something similar. I can see the paint falling under division 9 easily. But I’m curious about finishing an interior partition with a wood veneer. Does the veneer fall under 9?

I’m for the most part leaning on your side with wood veneer being 6 but thought I’d make it extra tricky. Let me know your thoughts.

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Hi @Shikha ,

I’m afraid there’s no hard and fast rule here - it depends on a number of factors. It depends both on what the product is and what its applied to. I would default to assuming anything with ‘wood’ in it is Division 6 unless other clues are given.

For example, wood veneer for cabinetry is division 6. Wood veneer panels are division 6. Doors with wood veneer are division 8. If it is truly an applied thin wood veneer then you likely are into division 9. Wood floor & ceiling tiles likely are 9 as well. And, some manufactures might put their composite product under division 10.

Check out Arcat’s list of products in divisions 6 & 9 for reference below:

Hope this helps!
-Darion