Passive solar heating studies at the Division of Building Research

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Passive solar heating studies at the Division of Building Research

Barakat, S. A.

ISSN 0701-5232

1:35u

PASSIVE SOLAR HEATING STUDIES AT THE D I V I S I O N OF BUILDING RESEARCH

by

$.A. Barakat

ANALYZED

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PASSIVE SOLAR EIEATING STUDIES AT THE D I V I S I O N OF BUILDING RESEARCH

S.A. Barakat

h part of the program of the National Research Council (NRC) to

evaluate passlve s o l a r heating techniques, a test f a c f l i t y was

constructed a t the Division of Building Research (DBR) t o obtafn data on

t h e t h e m 1 p e r f o m n e e of p a s s i v e l y heated structures and to d e v e l o p

simple calculation procedures and guidelines f o r designing houses wfth

p a s s i v e features. Thfa N o t e gfves the construction features and

instrumentation d e t a f l s of the passive solar t e s t f a c i l i t y and describes

t h e studies b e i n g undertaken at DBR r e l a t e d _{t o passive solar heating.}

1, INTRODUCTION

I n f o m a t i o n on the thermal, performance of passive solar h e a t i n g

can be obtained by nronitorlng eirher f u l l - s i z e o c c u p i e d houses ar

experimental test c e l l s . These is a considerable degree of uncertainty

iLn data f r o m occupied houses due to variations in occupant behadour,

O n rhe other hand, t e s t cell data cannot cover the range of conditions

that occur in larger structures, e s p e c i a l l y t h e interaction between

solar-heated zones and the remainder of the build1 ng, The test

b u i l d i n g s described in t h k s Note represent a f u l l - s c a l e s e c t i o n of a

house, combining t h e advantages of a controlled experiment with the

a b i l i t y to examine the i n t e r a c t i o n between south and n o r t h zones.

The experimental f a c i l i t y will provide data to aid in deremining t h e d y n a d c t h e m 1 characteristics of houses w i t h d i f f e r e n t amounts of

thermal mass. The data w f l l a l s o be used to v e r i f y the thermal

p e r f o m n c e p r e d i c t e d by hour-by-hour computer s i m u l a t i o n programs.

These programs, in turn, will be used to assess the performance of

passive sysrem and to compare p a s s i v e s o l a r techniques with o t h e r

energy c o n s e r v a t i o n measures under Canadian climatic conditions. The sirrmlation programs will also be used to d e v e l o p passive design

g u i d e l i n e s and a simplified procedure to calculate the apace heaolng

requirement of houses taking i n t o account s o l a r gain, thermal s t o r a g e

and allowable temperature swing,

The following sections describe the

Dm

o t h e r p r o j e c t s aimed at understanding and quantifying t h e perf errnance of

passive solar-heating methods.

DBR FASSIVE SOLAR FACILITY

2.1 Description of T e a t Facility

The test facf P i t y shown in F i g u r e s 1 and 2, is located on the _NRC

campus in O t t a w a ( e l e v a t i o n 114 m, l a t i t u d e 45'19' North, longitude

It consists of three huts d i v i d e d i n t o four 2-zone t e s t units

(numbered Unit 1 t o Unit 4 ) and four single-room units (RL t o R 4 ) . Each hut c o n s i s t s of a one-storey i n s u l a t e d wood-frame superstructure over a

basement. The exterior walls and the roof of t h e above-grade

c o n s t r u c t i o n have t h e m 1 resistance values of 2.1 and 3.5 u?- = O C / W ,

respectively. S i n c e t h e basements are Being used f o r t h e s t u d y o f

basement heat loss, he floors of the solar u n i r a wers i n s u l a t e d to a

resistance value of 7 u? *"C/W. A l l units and room were made as

airtkght as possible.

Each of t h e two-zone units c o n s i s t s of a south and a north room

w i t h a connecting door. The n o r t h room opens onto the corridor through

an i n s u l a t e d steel door (thermal resistance of 1.25 &*oc/w) f i t t e d

with magnetic edge seals. Each south room has a south-facing win do^ of

2.6 rn2 net glass area; each north room has a 1 m2 window f a c i n g n o r t h -

All the windows are of the casement t y p e containing sealed double- glazin w i t h an a i r s p a c e thickness of 6.35 rmn (thermal resistance of 0.35 mfm'C/W). The i n t e r i o r surfaces of a l l the walls and c e i l i n g s (other than mass walls) are finished with an off-white p a i n t and the

f l o o r s are carpeted.

The t h r e e "direct-gain" test units (Units 1, 2 and 3) d i f f e r only i n the type and amount of mass l o c a t e d i n s i d e t h e insulation layer, as shown in F i g u r e 3 . The interior f f n l s h of Unit 1, which represents a

conventional i n s u l a t e d wood-frame c o n s t r u c t i o n , consists of a s i n g l e layer of 12-7 rmn gypsum board. In Unit 2, a l l the i n t e r L o r w a l l

surfaces have a l i n i n g of four layers of 12.7 mm gypsum board while the c e i l i n g has a two-lager lining of the same material. In Unit 3 , a l l t h e

walls are lined with a 100 rsm course of solid cement: b r i c k s except f a t t h e wall between t h e south and north room which is made of a single

course of the same b r i c k , The amount of thermal storage contained in

the units is given in Table 1.

The mass-wall u n i t (Unit 4) has t h e same i n t e r i o r f i n i s h as Uni': 1 b u t has, In addition, a mass wall located just inside the windcw. This wall, which is made of s o l i d cement b r i c k s , is 0.305 m deep and has

two 406 tm by 7 6 tnm vent h o l e s at both t h e t o p and bottom, A p l a s t i c

sheet is suspended over the _{inner surface of both t o p vents to a c t as a}

back-draft damper. The outer surface of the mass wall is covered with a

f Pat black p a i n t .

The thennal interaction between a sunlit south room and the

r e m a i n d e r of a p a s s i v e l y heated house can be examdned in the f a c i l i t y by

monitoring each test unit in either of t w o modes, In the first mode the

u n i t 5 s monitored as two separate room; Fn the second mode the

connecring door is opened and air is c i r c u l a t e d between the two rooms

using a small f a n (2.8

2

The four single-room test units ( U n i t s R I to R4) have the same

i n t e r i o r f i n i s h as Unit 1. Each room has a w i n d m of 2 . 6

d-

Each of the rooms in the test facility is heated i n d i v i d u a l l y

avoid the temperature variations caused by convenrional room

thermostats. In addition, the south room af the two-zone units and

Ehree of t h e single-room units ( R l , R2 and FS) are equipped w i t h an exhaust fan which cools t h e room w i t h outdoor air whenever t h e roam temperature reaches a preset maximum. The exhaust f a n I s c o n t r o l l e d by the space-heater controller.

2.2 Measurement and Data Acquisition

The average indoor alr temperature of each room and the average temperature of the i n s i d e and outside surfaces of the mass w a l l are

measured with 1%-point and 9-point copper-constantan thermopiles,

respectively. Copper-constantan thermocouples are used t o determine the

attic a i r temperature, the c o r r i d o r aft temperature, the ventilation fan

inlet air temperature and the temperamre of the a i r flowing through the

vent h o l e s of t h e mass w a l l .

Three Eppley pyranometers are used to measure t h e i n c i d e n t solar r a d i a t i o n on t h e h o r i z o n t a l surface, the south-facing v e r t l c a l surface and the north-facing vertical surface. The d i r e c t normal component of

solar radiation is measured with an E p p l e y pyrhelfameter.

The e l e c t r i c a l space-heatfng energy consumption In each room is d e t e d n e d by means of a kW-h meter modified to generate a pulse

o u t p u t . Modif l e d kW*h rneters are a l s o used to record the energ)r

consumption of the cross-room circulation f a n s and t h e room-cooling

f a n s . Wfnd speed and d i r e c t i o n are measured on a 1 2 m h i g h weather tower at the s i t e .

An 80-channel M ~ n i t ~ r Lab data logger I s used to scan and record

the data on 9-track magnetic tape which is later p r o c e s s e d on an IBM 370

computes. Wind data, radiation data and temperatures are scanned every

minute, then averaged e v e r y 15 minutes and recorded. Pulse signals from

t h e m o d i f l e d k W m h meters are accumulated o n a p u l s e t o - a n a l o g u e Interface after which their totals are scanned and recorded every

15 dnutes.

The test f a c i l i t y building was completed in March 1980 and

e q u i p p e d s i x months later with full instmencation and a data

acquisition system. Data on the performance of the eight test units

were c o l l e c t e d during t h e 1980/81 heating season. Thrring the f o l l a w i n g

summer an e x t e r i o r l a y e r of i n s u l a t i o n was added t o the walls and c e i l i n g s of all t h e test unirs to b r i n g t h e i r t h e m 1 resistance t o 4.2 and 5.6 m2.'~/~, respectively. In December 1981, z n i g h t i n s u l a t i n g curtain was i n s t a l l e d on the window in f r o n t of the mass wall in Unit 4 .

Data have a l s o been gathered for t h e 198kJ82 heating season.

3 - PASSIVE SOLAR STUDIES

The results obtained in the passive solar t e s t f a c i l i t y form part

of s e v e r a l p r o j e c t s which are described b r i e f l y in t h e following

3.1 Evaluation o f Passive Solar heat in^ Techniques

The data collected on the test units during 1980/81 are being

analyzed t o d e t e d n e the energy-saving potential of d i f f e r e n t passive solar-heating techniques. Data gathered for t h e three direct-gain unfts

a r e being used t o study the e f f e c t of mass on solar gain utilization and energy savings, and on indoor temperature variation (overheating). The

data for the 1981182 heating season w i l l be used t o assess the savings

and overheating p o t e n t i a l in very w e l l Insulated passive houses.

The data on the masa-wall u n i t ( U n i t 4 ) w i l l be used to examine

t h e performance of a "TsornbeWall"' t y p e passive system under Canadian

climatic conditions. The effect on performance of the f n s u l a t f n g

c u r t a i n i n s t a l l e d in December 1981 wi 11 also be evaluated.

Future plans f o r the 4982/83 season include modificatians ta the

f a c i l f t y to assess the performance of attached sunspaces.

3 . 2 Study of t h e Dynamic T h e m l Response of Houses

Since the thermal response f a c t o r s available in the existing literatureP and used in energy calculatLon programs were derived for comnmercLa1 buildings with large amounts of t h e r m a l mass, the need

rematns ta determine the response factor for lighter constructions,

p a r t i o l d a r l y light-frame houses, in order t o simlate t h e i r thermal

performance.

Experiments are being performed in the three direct-gain passive

t e s t units to d e t e d n e dynamic thermal response f a c t o r s t h a t could be

appropriate for houses with three d i f f e r e n t levels of thermal storage

mass; namely, light, m e d i m and heavy. h e experiment consists of shading the south window for a long p e r f o d , then removing the shade f o r o n e hour to generate a sofar energy p u l s e i n p u t - By measuring the decay i n t h e space-heating requirement, the t r a n s f e r function (and hence, the response factors) of the room can be calculated,

The results of t h i s study w i l l be used to check the response f a c t o r s predicted by t h e room r e s p o n s e f a c t or calculation program.

Appropriate response factors w i l l then be used in the "ENCORE-CANADA"

and o t h e r available energy calculation methods to simulate t h e thermal performance of the three direct-gain u d t s . Finally, t h e

s i m u l a t e d and measured performances will be compared t o assess the a b i l i t y of these calculation methods t o s i m l a t e envelope L o s s e s , b u i l d i n g dynamics and s o l a r g a i n

3 . 3 Study of Solar Gain through Windows

In

t h e w i n d m s can contribute a large fraction of t h e heatfng requirement

of t h e house. The solar contribution can be enhanced through t h e use of

"improved" wimdms such as multiple-glazed windws, wlndms with

r e f l e c t i v e films, and glazed unfts with convection suppresston

techniques f a r improving t h e n e t h e a t g a i n through windows, t h e methods

to calculate the s o l a r heat gafn mst be updated and modified for

greater accuracy.

Determining the solar gain through windows consists of t w o calculations: f i r s t , t h a t o f t h e solar r a d i a t i o n i n c i d e n t on t h e outside surface of the window and, second, that of the amount of

i n c i d e n t solar energy transmitted through the window and absorbed by the

room. A brief deacriprlan of the work befng done to improve these

calculations f o l l m s .

In

c a l c u l a t e the solar radiation i n c i d e n t on t i l t e d surfaces from data

measured on the horizontal. This has given rise to the need to

d e t e m t n e how w e l l t h e s e m o d e l s p r e d i c t the solar energy i n c i d e n t an

vertical surfaces, The solar radiation values measured on the

h o r i z o n t a l surface at the passive s o l a r t e s t f a c z l f r y will be used to

calculate, with the help of the models, the solar radiation i n c i d e n t on

vertical-south and vertf cal-north surf aces. The accuracy of each model

will be determined by comparing the calculated values with the measured

values. The b e s t model w i l l 1 subsequently be i n c o r p o r a t e d into various

energy calculation programs.

A computer program has also been developed to calculate the net solar heat gafn through s i n g l e , double-, and t r i p l e g l a z e d windows for

1 3 Canadfan l o c a t i o n s 3 * 4 . _The program will be updated to i n c l u d e

calculations for the s o l a r gain through other glazfng t y p e s (quadruple-

g l a z i n g , windaws w i t h r e f l e c t i v e film and honeycomb windcws)

,

as t h e effect of shading from overhangs and window frames, Ways t o a c c o u n t f o r t h e short-wave. r a d i a t i o n r e f l e c t e d o u t of rooms through wfndows will also be s t u d i e d .

3.4 Development of Passive S o l a r Design G u i d e l i n e s and Calculation Procedure

A simple method to estfmte the heating energy requirements is

needed to compare t h e energy consequences of a v a r i e t y of house designs

as well as to evaluate the compliance of these d e s i g n s with energy s tandards

.

An Important component In an energy calculation method of this

n a t u r e , particularly f o r passive solar houses, is the amount of s o l a r

energy gafned through t h e windows and u t i l i z e d t o o f f s e t the heat

l a s s e s , Only a fraction of t h e solar energy g a i n e d can be u t i l i z e d .

The magnitude of t h i s fraction depends on a number of f a c t o r s includSng

geographical location, size and type of g l a s s , over-all b u i l d i n g heat

l a s s , thermal storage properties of the house, and the allowable rise i n i n d o o r temperature.

The object of t h i s study is to develop a simple method far

estimating t h e utilization of s o l a r g a i n through wiadcrws in all types of

houses in a l l clfmatic regions of Canada. This method has been d e r i v e d

from a l a r g e number of detailed computer s i m l a t i o n runs and is being

ultimately be used to develop g u i d e l i n e s for the design of passive solar

buildings.

The ultimate a i m of the DBR p a s s i v e solar program fs to a s s t s t b u i l d i n g designers in producing more e n e r g y - e f f i c i e n t homes t h a t do n o t

sacrTfice indoor thermal comfort. This will be achieved by developing

design g u f d e l i n e s and a simple c a l c u l a t i o n procedure for t h e v a r i o u s

phases of the design process. An important element of t h i s e f f o r t is

t h e generation of r e l i a b l e , pertinent data to v e r i f y these design

methods and, in general, ta aid in the evaluation of passive solar-

heating techniques.

REFERENCES

1. ASHRAE Handbook and Product Directory, Fundamentals, Chapter 22,

American S o c i e t y of Heating, R e f r i g e r a t i o n and Air Conditianfng

Engineers, New Yosk, 1977.

2. Konrad, A . , and B.T. Larsea, ENCORE-CANADA: Computer Program for

t h e Study of Energy C o n s m p t i o n of Residential B u i l d i n g s in Canada, DBR P a p e r No. 859, NRCC 17663, D i v i s i o n of B u i l d i n g Research,

National Research Council Canada, O t t a w a , 1978.

3. Rarakat, S . A . , Solar Heat Gafns through Windows in Canada, DBR

P a p e r No. 944, NRCC 18574, Division of Building Research, National Research Council Canada, Ottawa, 1980.

4 . Barakat

,

Windows, DBB Computer Program No. 4 7 , D i v i s l o n e f B u i l d i n g Research, National Research Council Canada, Ottawa, 1980.

5 . _{Barakat, S.A., and D.M. Sander, U t i l i z a t i o n of Solar G a i n s through}

Gllndms for Heating Houses, Buildtng Research Note 184, Division of

Table 1

TTEXHAL

Test Storage W s s (Kg)* Heat Capacity (MJ/K)

U n i t Type South Room T o t a l Unit South Room T o t a l Unit

1 DG, L i g h t 645*** 1308 0,75 1.53

2 DG, Medium 1810 3704 2.03 4.13

3 DG, Heavy 7435 13565 6 -33 11.55

4 Mass Wall** 4 200 4866 3.70 4.48

*

**

( a )

N O R T H

'T<

( b )

4 3.5 INS91 VAPOR BP9TlER 9-r, 1. I2 I mrn G Y P j U M 'I

-11

1 , ;

3