Energy Site Management

ENERGY SITE MANAGEMENT EQUATION & A PROPOSED PROCESS TO ESTABLISH ENERGY BALANCES ON SITE

Solar energy is the source of life and the principal factor of evolution and its interaction with site massing remains inevitable. As we transform the natural environment to our needs, we introduce hard surfaces such as roads, walls, widows and roof; they all absorb energy by radiation which transfer the heat at different rate and different time by conduction as well as release heat by convection. Also the structure requires energy for heating and cooling system to function thus a bigger quantity of energy or heat is produced and transferred back to the living site.

It is essential to reveal how the footprint and massing of a site manage the quantity of solar energy at pre-development state and compare them to the quantity of energy that the same site is going to produce after development. By subtracting the comparative results, we will discover the additional quantity of energy that site must manage therefore taking necessary measures to establish the natural balance of energy management on site.

The following study has been pursuit to explore energy site management equation prior and after development. The focus will be only on what quantity of solar energy that site and exterior envelop attract and as designer what measures we need to take to regulate the energy balance as it was at pre-development state. The energy required for basic function of the envelope and its production on site is subject to a separate study and it would not be included in the calculation because the necessary energy to be produced is equivalent to the energy that the envelope will consume independently.

For study case I have chosen a typical existing single family residence in phoenix area:

Lot size 7,000 sf, building footprint 1,500 sf, east west oriented, climate zone 2,July 31st at 12PM, sun altitude 80^o south. The warmest day in summer is chosen as the base for calculation,the radiation effect on various sides of a building is expressed in KBtu / ft²/ Day per below chart.

Orientation – Phoenix Area	KBtu / ft ²Day

East wall	1.207
South wall	0.563
West wall	1.207
North wall	0.452
East wall	1.207
Roof & horizontal surface	2.596

*Reference: Design with Climate, Victor Olgyay

Step 1 – Inventory of energy on site at pre-development state:

a) Research historic data, referring to title and survey plan, we may find out waht site used to be at natural state.

b) Calculate the surface area considering the amount of solar energy that site is receiving,reflecting and absorbing at natural state.

Since the solar reflectance energy is reflected and not retained on site, we should focus on the portion that site absorbs and releases with lag time. We should also consider the amount of energy that is not reflected therefore is absorbed.

Material	Surface area SF	SRI in. %	Absorpt. %	Calcs KBtu / Day

Site horz. surface Light colored soil	70’x100’ = 7,000 – 226 = 6,774 Site – tree shade area	45	55	2.596 x 6,774x 0.55 = 9,672

2 Exist. Deciduous trees 12’ Dia	2 x 113 = 226	18	82	2.596 x 226 x 0.82 = 481

Total energy attracted on site @ pre-development state				*Inventory* 10,153

***Approximate albedo of light colored soil surface = 0.4 – 0.5

Within pre-existing Macroclimate, we have just discovered the amount of energy that site was generating and processing. As we modify a site, we create a Microclimate at the scale of site attracting more energy means producing more heat and enforcing Heat Island Affect.

The challenge will be to balance the total amount of energy on site with implementation of measures and strategies for proposed site and envelope therefore 10,153 KBtu / Day remains as a reference.

Step 2 – Survey of Existing Condition:

To survey and calculate the surface area of existing condition considering the amount of solar energy that is attract by site surface, site features and the existing envelope to reveal the total amount of attracted energy on site.

*Site*	*Surface area* SF	*SRI. %*	*Absorpt. %*	*Calcs* KBtu / Day
Conc. Fence E.	6’ x 90’= 540	25	75	1.207 x 540 x 0.75 = 489

Conc. Fence S.	6’ x 20’ = 320	25	75	0.563 x 320 x 0.75 = 135

Conc. Fence W.	6’ x 90’= 540	25	75	1.207 x 540 x 0.75 = 489

Conc. Fence N.	6’ x 20’= 120	25	75	0.452 x 120 x 0.75 = 41

Conc. pads	625+125+600=1,350 Minus 290 shaded Area on North of bldg.	20	80	2.596 x 1,060 x 0.80 = 2, 201

4 Exist. Trees 25’ Dia.	4 x 113 = 452	15	85	2.596 x 452 x 0.85 = 997

Remaining Site Surface	7,000–1,740-1,350-1,963-1,350-390 = Site–roof area-tree’s area-conc. pads-shades areas	45	55	2.596 x 1,557 x 0.55 = 2,223
*Building*	*Surface area* SF	*SRI. %*	*Absorpt. %*	*Calcs*
Medium dark paint / stucco – East	420 sf wall. 24 sf window	20 –	80 71SHGC trans.	1.207x420x 0.80 = 552 1.207 x 24 x 0.71 = 20

Medium dark paint / stucco South	632 sf wall. 80% of south wall shaded by overhang includ. windows Count 50% of SHGC 144 sf window	20 –	80 71SHGC trans.	0.563x420x 0.80 x 0.80 = 324 0.563 x 144x 0.80 x 0.50 =32

Medium dark paint /. stucco West	420 sf wall. 24 sf window	20 –	80 71SHGC trans.	1.207x420x 0.80 = 552 1.207 x 24 x 0.71 = 20

Medium dark paint / stucco – North	632 sf wall. 144 sf window	20 –	80 71SHGC trans.	0.452 x 632 x 0.80 = 229 0.452 x 144 x 0.71 = 46
Roof w. gray asphalt singles	58 x 30 including Overhang	13	87	2.596 x 1,740 x .87 = 3,930
Total				11, 626 KBtu / Day
Total energy surplus on site @ existing condition				11,626 -10,153=1,109 KBtu/Day

*Reference: Mechanical and Electrical Equipment for Buildings, Benjamin Stein, John S. Reynolds @ other sources

Step 3 – Comparing inventory with survey of existing conditions

: By subtraction the results reveals we have an excess of 11,626 -10,153 =1,473 KBtu /Day

At this point we should consider regulating site energy balance by surface improvement, landscape area and body of water, we should also revise the material of the exterior envelop for a better site energy balance.

Step 4 – Design Concept:

Selecting material with high albedo meaning less absorption; providing trees and shading, green cover, replacing aged concrete with new light color pavers and so on.

*Site*	*Surface area* SF	*SRI. %*	*Absorpt. %*	*Calcs* KBtu / Day

Conc. Fence E. White acrylic paint	6’ x 90’= 540	80	20	1.207 x 540 x 0.75 = 489

Conc. Fence S.	6’ x 20’ = 320	80	20	0.563 x 320 x 0.75 = 135

Conc. Fence W.	6’ x 90’= 540	80	20	1.207 x 540 x 0.75 = 489

Conc. Fence N.	6’ x 20’= 120	80	20	0.452 x 120 x 0.75 = 41

Conc. Pads Replaced w. clear conc. pavers	625+125+600-285 –290 =775 Minus 290 shaded Area on North of bldg. Minus 285 tree shade	70	30	2.596 x 775 x 0.80 = 604

4 Exist. Trees. Added 15 new Trees, 4 +15=19	19 x 113 = 2,147	18	82	2.596 x 2,147 x0.82 = 4,570

Green ground cover	850 – 500 = 350 Ground cover – tree shade area	20	80	2.596 x 350x 0.80 = 727

Pool clear background	35 x 20 = 700	8	92	2.596 x 700x 0.92 = 1,672

Decomposed white granite cover	2,120 – 1,465 = 651 DG’s Cover – tree shade area	60	40	2.596 x 651x 0.40 = 676

*Building*	*Surface area* SF	*SRI. %*	*Absorpt. %*	*Calcs*

clear paint / stucco – South	632 sf wall. 100% of south wall shaded by overhang & 50% of the wall is shaded by trees – Count 50% only for radiant energy for South wall Windows Count 50% of SHGC 144 sf window	80 –	20 39 SHGC trans.	0.563x632x0.20×0.50=36 0.563 x 144x 0.39 x 0.50 =16

clear paint / stucco – West	420 sf wall. 24 sf window Minus 50% shaded wall	85 –	15 27SHGC trans.	1.207x420x 0.15x 0.50 = 38 1.207 x 24 x 0.27 = 8

clear paint / stucco – North	632 sf wall. 144 sf window 100% of North wall shaded by overhang & 30% of the wall is shaded by trees – Count 50% only for radiant energy for Notrh wall Windows Count 50% of SHGC	80 –	20 71SHGC trans.	0.452x632x0.20×0.50 = 29 0.452x144x0.71×0.50 = 23
Cool Roof	58 x 35 = 2,030 Include. Extended Overhang 50% of roof is shaded by trees	80	20	2.596x2030x0.20×0.50= 527
Total				10,126 KBtu / Day
Total energy surplus on site @ existing condition				Study Case Result: 14,031 -9,995 = 4,036 KBtu /Day

Step 5 – Design comparasion at different stages:

At pre-existingstate within natural environment site was generating:

10,153 KBtu / Day

At existing condition with envelope & other features site was generating:

11,626 KBtu / Day

At design case with material revision and site improvement site in generating:

10,126 KBtu / Day

Conclusion: At the design case calculations indicate that site s less than once it used to be part of natural environment despite we have built-in an envelope on. We can conclude the energy site management equation and the proposed process works.