ventilation rates

[r.bartlett]

we were asked to quote out a new function facility and was told to expect 140 people. we naturally worked on 10 l/s, heating at 40kw only: no cooling which was a concern

and came out at 50k approx for the job.

the recommended unit from the consultant came back at 4 l/s per person and hence we were miles out (more than double budget)

Is there a way of reducing air volume in a sealed space for that number of people as it's left me confused

[Tesla]

Sorry Mr. Bartlett, but 10 is 10 and 4 is 4. You could try to use energy/heat recovery on that additional fresh air from the spill air or control to co2 which may be in between.
Your quote should have stipulated (based on 10) as there is no assumption on contracts only interpretation and it should have been in the tender as 41. If there are no penalties you could default or re negotiate if it was not clearly stated in documentation.
I guess by reading your post several times now we are talking about recirc rates not fresh air. Even so there are some diffusers which are much more efficient than others with different applications based on geometry such as height and height to floor ratios.
The rated flow rates etc. should be from standards for the activity or process taking place.

[Rob White]

Sorry Mr. Bartlett, but 10 is 10 and 41 is 41. You could try to use energy/heat recovery on that additional fresh air from the spill air or control to co2 which may be in between.
Your quote should have stipulated (based on 10) as there is no assumption on contracts only interpretation and it should have been in the tender as 41. .

I read Richards post as 10 l/s and 4 l/s, FOUR l/s.

Regards

Rob

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[r.bartlett]

I read Richards post as 10 l/s and 4 l/s, FOUR l/s.

Regards

Rob


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Indeed Rob, 10 l/s fresh air per person against the consultants 4 l/s on full heat recovery with hot water heater battery

[frank]

Got to ask Richard.... how does a fan/unit doing 1.4m3/s and a LTHW coil installation equate to a 50k job?

Was there a large amount of ducting involved?

I agree with your calcs that 140 people @ 10l/s fresh air would need 40kW of tempering (-3 to + 20C) but the Consultants requirement for only 4l/s surely wouldn't reduce the job cost by half? Fan/unit + ducting etc still required.

All the fresh air rates in CIBSE etc are only for guidance and good practice so it is difficult to justify his requirement against your assumption based on good practice