2_4 Gutter and Downspout Sizing and Location.xls

8/17/2019 2_4 Gutter and Downspout Sizing and Location.xls

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2.4 Gutter and Downspout Sizing and Location Calculations

Both Metric and English units: Ree!er to sa"e this spreadsheet to #our own coputer.

We will use the larger of the two or 310 sq ft for our first calculation.

First we will find the maximum amount of rain that will be captured in gallons per minute

Enter the plan area of your first roof section(s in square feet here 310 sq feet !"." sq m

#.$% inches&hr !.0 mm&min

'ross gallons per minute 1%.3

'ross )iters per minute %"

*ssumed collection efficiency "% percent

+et gallons per minute 13.0

+et liters per minute #,

-his spread sheet will help you calculate the gutter width and maximum distance between downspouts based on your maximum rainfall roof area and stof gutter. -here are two ma/or factors to consider when deciding a gutter design. -he first is to mae it wide and deep enough to collect all of the rainwaduring the hardest rainfall. -he second is to slope the gutter downward enough to allow good drainage and flow but not so much that you drift so far belohe edge of the roof that the water oershoots the gutter. We will calculate both simultaneously for you.

We will present calculations for four common gutter designs2 a semicircle a trough of which you can ery the inside angle2 a box (square trough and arape4oid.

$irst: We5ll decide what area of the roof is applicable to the calculations. -his will dictate the amount of water that the gutter needs to be able to carry du

he hardest rain storms. *s you proceed eep in mind the different areas of your roof that you measured in section !.! 6alculating your roof area forainwater haresting.

Second: We will enter data about your highest intensity of rainfall followed by an assumed gutter efficiency and finally the friction factor of the material tyou will mae your gutter out of.

%hird: 7f the distance between downspouts turns out to be too short for your home we will let you enter trial gutter widths until the length drop and widthwor well with each other.

$ourth: We5ll discuss your downspout si4e location and a few comments.

8esults will be tabulated so that you can easily see results as you change ariables. 9etail drawings and dimensions will follow the table for each of thegutter designs.

$irst: 'et the dimension of the roof areas that you want togutter. -hese are the areas that you calculated in section 2.2Calculating your roof area for rainwater harvesting . We are goingo assume that alues are in feet and square feet. *s a reminderhe areas are *a at !%! sq ft : 335 long ;b at 1,0 sq ft : 1%5 6c

at 1!0 sq ft : 105 and 9d at !#% sq ft : !,5.

We are going to assume that you want to mae your guttersaround your home loo the same as far as material ofconstruction width and design are concerned. -his allows us tosi4e the gutters based on the longest length betweendownspouts. *ny shorter lengths of gutter will hae no problemhandling the water olume or the slope. se these

default numbers if you can5t find this data for your location.

+ote? 9on5t mae this number too small we are already assuming a 3 full gutter at itmaximum depth. -his efficiency number is to tae care of splash and gable losses.


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@aterial

8ough sandy or bumpy material lie bamboo rough wood or shingles 0.0$

8elatiely smooth wood 0.0#

'alani4ed metal 0.0!

ery smooth material lie plastic 0.01

Enter the friction factor from this list here AAB 0.0!

0.% degree -he drop is calculated here for you

slope the first !&3 of gutter farthest from the downspout # mm & meter 3&1C in & yard 1 ? !!,

slope the last 1&3 of gutter length /ust before the downspout , mm & meter %&1C in & yard 1 ? 11%

inches mm feet meters mm inches meters feet m

=emi 6ircle inches ! "&" ,0 !C.C ".1 100 3 1&" ,.% 31.! 1%,0 degree -rough 3 0&" ,# !"." "." 100 3 1&" ,.% 31.! 1#

=quare ;ox 1 3&" #1 1.C 0.% 100 3 1&" ,.% 31.! 30-rape4oid ! 3&" $# 1".C %.$ 100 3 1&" ,.% 31.! 1%

1

!

3

+ow decide on the material that the gutter will be made out of. We need this information to establish a friction factor forour calculations. Dou will find that the rougher the gutter material the larger the gutter will need to be. -he default frictionactor of 0.0! is entered for galani4ed metal. =imply select your friction factor from this table and type oer the 0.0!

already entered in the yellow box.


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-hese are dimensions based on the larger gutter width needed for longer distances between downspouts

-hese are dimensions based on the @inimum 'utter Width needed to carry the water

! "&" /n /nches *hat0i' "alues

=emicircle width ! "&" in # #&" 3 1&" in # ,

Seicircle Gutter inches! 1&" in ! #&" in

1 %&" in 1 $&" in

!C.C feet 31.! ft

,0 /n *hat0i' "alues

=emicircle width ,0 mm 1#1 100 mm 1%

Seicircle Gutter

C$ mm $$ mm

#$ mm %% mm

".1 meters ,.% @

/n /nches *hat0i' "alues

3 0&" -rough inside wall length ! 1&" in # !&" ! !&" in # %

! 1&" ,0 ! 1&" -rough top opening width 3 0&" in 3 1&" in

1 %rough inches

! 3&" in ! #&" in

1 C&" in 1 $&" in

!"." feet 31.! ft

/n *hat0i' "alues,# -rough inside wall length C$ mm 133 $1 mm 1#

C$ ,0 C$ -rough top opening width ,# 100 mm

1 %rough

$1 mm $$ mm

%1 mm %% mm

total width of rawbuilding material needed

to mae this gutter

=ubtracting 3G under theroof edge and 1&"G outsideedge allowance

this is the width that is aailablefor the rainwater to enter thegutter

wida

piecbuimat

@aximum --*) gutter dropbefore any downspout

-his assumes #.$G per hourmaximum rain intensity.

@aximum distance to firstdownspout

9on5t forget that one downspoutcan hae this length of gutter onboth sides of it (put thedownspout in the middle

total mm width of rawbuilding material needed

to mae this gutter

=ubtracting !0mm under theroof edge and 3mm outside

edge allowance

this is the width that is aailablefor the rainwater to enter

@aximum gutter drop beforeany downspout

-his assumes ! mm per minmaximum rain intensity.



total width of material 7f you are going to use

something thic lie

wood remember to addthe thicness of the

wood to one side length



wida

piecbuimat






something thic liewood remember to add

the thicness of thewood to one side length

=ubtracting !0mm under theroof edge and 3mm outsideedge allowance





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"." meters ,.% @


=quare box height and width 1 3&" in 3 ,&" 3 1&" in ,

1 3&"

1 3&"

S&uare Bo( inches C&" in ! #&" in

1&" in 1 $&" in

1.C feet 31.! ft

/n *hat0i' "alues

=quare box height and width #1 mm 1!3 100 mm 30

#1

#1

S&uare Bo( 1" mm $$ mm

3 mm %% mm

0.% meters ,.% @


! 3&" 1 !&" in3 %&"

0&0 in # $

!&" 1 !&" -he width at the top is ! 3&" in 3 1&" in

1 !&"

1 C&" in ! #&" in

%rapezoid inches 1 0&" in 1 $&" in

1".C feet 31.! ft

/n *hat0i' "alues

$# 3$ mm 111 %0 mm 1%




something thic liewood remember to addtwo times the thicness

of the wood to thebottom length



wida

piecbuimat








=ubtracting !0mm under theroof edge and 3mm outsideedge allowance





9on5t forget that one downspoutcan hae this length of gutter onboth sides of it (put the

downspout in the middle

With sides at 30 the lengthof each side is




30

=ubtracting 3G for under the

roof edge and 1&"G outsideedge allowance

this is the width that is aailable

for the rainwater to enter thegutter

wida

piecbuimat



@aximum gutter length to adownspout


With sides at 30 the lengthof each side is



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3$ 3$ -he width at the top is $# mm 100 mm

3$

%1 mm $$ mm

%rapezoid 33 mm %% mm

%.$ meters ,.% @



30

=ubtracting !0mm for underthe roof edge and 3mmoutside edge allowance





9on5t forget that one downspout

can hae this length of gutter onboth sides of it (put thedownspout in the middle

$ourth: Downspout size+ location+ and a 'ew other coents.

don5t recommend that you si4e your downspout based on pipe si4ing tables or equations. 7 recommend you go outside and loo at trees that oerhang oof. Dou5ll need to put in a downspout that won5t clog with the leaes that are going to land on your roof. For most of you that will be a # inch or 110mm

pipe. Dou might need to mae this out of a piece of flexible material. =imply bend it into a semicircle with a diameter that is about the same si4e as thesemicircle dimension that was calculated for you aboe. -his will be plenty big for both the water and debris. Dou might want to isit the gutter manufactweb sites to get an idea of how they would si4e a downspout.

http?&&www.hunterplastics.co.u&rainwater&gutterdesign&default.html

http?&&copper.org&applications&architecture&archLdhb&guttersLdownspouts&downspouts.html

http?&&members.o4email.com.au&Msengs&9

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2_4 Gutter and Downspout Sizing and Location.xls