ARCH-432

Conduction Cooling Loads

First Exam

October 14th

Hot Glasshttp://www.theguardian.com/artanddesign/2013/sep/06/walkie-talkie-architect-predicted-reflection-sun-rays

Lotus Temple or Baha'i Temple

http://www.bahaihouseofworship.in/architectural-blossoming

Attendance

What amazing improvement did the ancient Romans make to Greek architecture so their homes (called heliocaminus, i.e. house furnaces) were far more energy efficient?

A. Used cavity wallsB. Made domed roofsC. Insulated the wallsD. Put transparent mica in the windowsE. Honeycombed the floor

Attendance

Put transparent mica in the windows.In some rare occasions, glass in the South facing windows trapped the heat inside the home. The home pictured dates from the first century B.C. and is a typical heliocaminus.

heliocaminus

heliocaminus

What You Need to Know

Describe the components that make up a cooling loadUnderstand the fundamental differences between heating and cooling loads

What You Need to be Able To Do

Calculate simple conduction cooling loadsEvaluate systems to identify energy savings

Terms

Cooling loadTotal Equivalent Temperature Differential (TETD)Storage effectTime LagThermal mass

Cooling Load

“The amount of energy that must beremoved from a space in order to maintain the space within the comfort zone.”

Good News!

Same ‘R’ valuesSame ‘U’ valuesSame conduction heat transferSame convection heat transferSame radiation heat transfer

Cooling Load Componentsroofroof

lightslights

equipmentequipment

floorfloor

exteriorexteriorwallwall

glass solarglass solar

glassglassconductionconduction

infiltrationinfiltrationpeoplepeople

partitionpartitionwallwall

Sensible and Latent Gains

sensibleload

latentload

conduction through roof, walls, windows, and skylightssolar radiation through windows, skylightsconduction through ceiling, interior partition walls, and floorpeoplelightsequipment/appliancesinfiltrationventilationsystem heat gains

cooling load components

Major Differences from Heating Loads

Peak conditionsHeat storage effectConsideration of both latent and sensible gainsMore unique sources of heat gain

Time of Peak Cooling Loadh

eat

gai

nh

eat

gai

n roofeast-facing

window

12 6 12 6 1212 6 12 6 12noonnoona.m.a.m. p.m.p.m. midmidmidmid

Storage Effect (thermal lag)

Prof. Kirk’s one-of-a-kind, surefire process guaranteed to result in a mind-numbing law suit.

CenterStone Building

August 24 start dateDec. 31 completion dateHeat turned on the first week of December

Thermal Mass Dilemma

Time Lagso

lar

effe

ctso

lar

effe

ct

12 6 12 6 1212 6 12 6 12noonnoona.m.a.m. p.m.p.m. midmidmidmid

AA BB

time lagtime lag

Time lag!

Conduction – Sunlit Surfaces

Total Equivalent Temperature Difference (TETD) is used to account for the added heat transfer due to the sun shining on exterior walls, roofs, and windows, and the capacity of the wall and roof to store heat. The TETD is substituted for T in the equation for conduction.

Q = U A TTETD

Conduction Gains(Walls and Roofs and doors)

Q = U x A x TETD

where TETD is the Total Equivalent Temperature Differential, which accounts for

Temperature difference Mass Color Solar Gain

Step #1 – Select Wall Type

Step #2

Select Sun timeSelect color of wall D = dark L = light

Select wall orientation

Step #3 – Read Value of TETD

Same Steps for Roofs

For Windows

Btuh = (U x A x TD) + (A x SC x SHGF)

A= AreaTD = outdoor design – indoor design temp.SC = shading coefficient SHGF = solar heat gain factors

EQ Credit 8.1 - Daylighting

ASHRAE Standard 90.1 10% lighting load

credit for harvesting

10% lighting load credit for occupancy sensors

Heat Gain from People

A function of activityAlways contains both sensible and latent components

Equipment - Office

Best obtained from manufacturersCan be reduced by using Capture HoodUsually is sensible, but may have a latent component

Equipment Loads (ASHRAE Fundamentals)

Ventilation Load

Must consider both sensible and latent loads

QS = 1.1 x CFM x (T2 – T1)

QL = .68 x CFM x (W2 – W1)

QT = QS + QL