Table 1-8 Recommended Building Thermal Envelope For New Construction
Degree-Days
Wall "U"
Glass "U"/SC
Roof "U"
Floor "U"
3000 & Below
0.27 (0.13)
1.50
0.10 (0.05)
0.24 (0.12)
(0.75)/0.40
3001 to 5000
0.20 (0.10)
0.80
0.10 (0.05)
0.20 (0.10)
(0.40)/0.50
5001 & Above
0.14 (0.07)
0.70
0.06 (0.03)
0.16 (0.08)
(0.35)/0.33
(b) Notes:
(1) The degree-days are based on the heating season when outdoor
temperatures are below 48 degrees C (65 degrees F), in accordance with
ASHRAE Handbooks-Fundamentals and Systems.
(2) The SCs of the glass windows are based on the intrinsic property of
the glass material only, that is, without any assistance from the
external shading devices, such as, venetians blinds and/or curtains.
(3) Insulating glass with lower "U" value might be necessary to prevent
condensation while maintaining the required 30 percent Relative
Humidity (RH) in perimeter spaces with 4 degrees C (25 degrees F)
outdoor design temperature and below.
(4) The "U" values are expressed as W/Hr/Sq M/ degrees C (BTUH/Hr/ Sq
Ft/degrees F).
(5) The "U" values are for floors of heated spaces over unheated areas,
such as sub-basements (pipe basements), garages, crawl spaces, etc. The
requirements of insulation for the slabs-on-grade for the heated spaces
are shown under perimeter insulation.
(c) Table below lists Overall "Uo" Factors and Degree Days:
Table 1-9 Recommended Overall "Uo" Factors for New Construction
Degree-Days
Uo (Overall)
3000
& Below
0.73(0.36)
3001
to 5000
0.63(0.31)
5001
& above
0.57 (0.28)
Uo =
Uw x Aw + Ug x Ag+ Ud x Ad
Ao
Uo
=
Overall Transmission Factor
Ao
=
Overall Gross Wall Area
Uw
=
Wall "U" factor
Aw
=
Wall Area
Ug
=
Glass "U" Factor
Ag
=
Glass Area
Ud
=
Door "U" Factor
Ad
=
Door Area
HVAC DESIGN MANUAL
1-27
GENERAL REQUIREMENTS
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