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1948-49 Theatre Catalog, 7th Edition, Page 453 (440)

1948-49 Theatre Catalog, 7th Edition
1948-49 Theatre Catalog
1948-49 Theatre Catalog, 7th Edition, Page 453
Page 453

1948-49 Theatre Catalog, 7th Edition, Page 453

the stage at the lowest level Where installation may be practical. In this respect, therefore ttT.L" is at variance with the principles of air distribution and the results of our experience.

On the other hand, he is right when criticizing the abSence of any provision for exhaust ventilation and-if I understand correctly-for fresh tlmake-upil air. In order to provide sufficient internal pressure in the enclosure to lower the neutral zone even below iioor level, more air must be supplied than is returned to the air conditioning unit. The excess air may then e'xfiltrate either into the theatre lobby or to the outside, and fresh air must be used to make up for such exfiltration losses. A ratio of 75 per cent return air and 25 per cent fresh air will usually produce satisfactory results.

Another important aspect of this problem is proper selection and location of air supply outlets in the rear of the theatre. due to the comparatively low ceiling height and the (presumably) large amount of air to be handled. If ceiling air distribution is not possible for structural reasons, wall type diffusers may be required to accomplish draftless air distribution in that section# E.G.

N.F. suggests a new layout-an air tunnel down middle or side of house.

It appears from the general information given by ttT.L." that a theatre 51 ft. wide x 188 ft. long and with a ceiling height at the rear of 8 ft., sloping down to 25 ft., that sidewall outlets would never give satisfactory air distribution.

These sidewall outlets would have to have a blow of 25 ft., 6 in. Even break< ing these up into many small units, the drop for that length of blow would be around 7 ft. and the air would surely impinge on the faces and bodies of the occupants.

It is my opinion that a much more satisfactory layout, as far as supply outlets are concerned, would be to locate

them down the center of the ceiling. The use of, say, four ceiling supply outlets would make for a good distribution without the danger of objectionable drafts.

As far as the return air is concerned, there has never been any definite information (to my knowledge) that establishes any particular location as being the most satisfactory solution for all returns. However, for winter use, there is a definite advantage for the stage return grilles, as there is a natural tendency for colder air to settle toward the front, which is taken up by these grillesethus preventing cold pockets in this area.

I used the following returns in past experience with very good results and I believe this scheme could well be adapted for this installation:

In theatres of this type where the floor is built directly on the ground, without basement space, we have dug a tunnel down either the middle of the house or on either side of the house. This tunnel is made of cinder, cement block, or tile pipe of proper area and was usually installed within a very short time without seriously disrupting operation, usually during the night. Into these tunnels we plugged either mushrooms or aisle type intake grilles.

I feel that the above suggestion, which I have found many times in many installations operates completely satisfactorily, would be a good solution for *" problem.eN.F.

R.R. says, distribute air from rear of theatre.

I agree with the conclusion of ttT.L.i, that the system as described to both heat and cool the theatre would be faulty and unsatisfactory. In my opinion, if the theatre is conditioned by the described system of using high outlets along the sidewall with returns along the front, two objectionable conditions would be repeated which have been found by experience in conditioning theatres in the past years. One of these


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conditions is that the rear of the theatre under and above the balcony will be inadequately cooled or overheated, depending upon the season. The second of these conditions is that of overcooling at the front of the theatre because the slope of the fioor causes the cooler air to collect there, independent of the season. These conditions may be corrected by the application of the best practices in air distribution for theatres, with which ttT.L." is apparently quite familiar. However, my suggestion for such a size theatre would be to distribute the air horizontally at a relatively high velocity from the rear of the theatre and high across the entire width. This high velocity movement of air would cause forward movement of the air high above the occupied area. Most of the air enters the system again at the rear for recirculation and the remainder goes out into the hall and lobby. This eliminates the objectionable conditions mentioned and does away with any possibility of having drafts striking the occupants on the back of the necks.

ttT.L,, also mentions that there is no provision for exhausting the ventilation or fresh air. In my opinion, this is quite acceptable as some of the air from the theatre auditorium should move from the rear of the auditorium through the hall and lobby onto the sidewalk, and this cannot be accomplished by having air exhausted directly from the theatre auditorium itself to the outdoors during the heating and cooling seasons. eRB.

In November, the problem was still very much in prominence.

There was published in the July issue of HPAC a question from ttT.L." (a consulting engineer) regarding air distribution in a theatre.

Because of the apparent interest in this question, WILL." has prepared the accompanying sketch (Fig. 3, the dimensions varying somewhat from those given in July). He writes as follows:

ifThe problem is to heat and cool the theatre and lobby by side wall outlets. About 25 per cent of fresh air is assumed to be taken into the equipment.

ttNo provision is made to exhaust the fresh air thus taken in. No provision is made to circulate all outside air.

ttAll return air is to be taken into inlets at the stage and returned to the equipment.

"In my opinion, the requirements are such that efficient air conditioning, either heating or cooling, would be impos-, sible. I therefore declined to attempt such a design.

ttThe architect claims that 'experts, have assured him of satisfactory and efhcient results. This is contrary to anything I might know about air distribution and the results actually desired or that should be obtained.

HApparently this problem is of interest to a number of HPAC's readers. Their comments and suggestions are of real interest and value to me as well as many others."

G.T.L., of Buenos Aires, faced the same problem years ago.

I read with interest the question of the month about return air intake location in theatres in the July issue as I

1948-49 Theatre Catalog, 7th Edition, Page 453