A difficalt case: Radiant floor + Nat Vent LEED increased ventilation credit requires that when using the macroscopic airflow simulation compliance path for naturally ventilated spaces: 1) 90% of the occupied spaces are prooven to be able to provide the required ventilation requirements as per the chosen standard (normally 62.1) 2) these ventilation requirements should also be consistantly applied to the energy model of EAp2 (note only occupied spaces are considered) 3) LEED has additional exhaust requirements for contaminated spaces (if IAQc5 is aimed for), which must also be considered by the increased ventilation credit and EAp2 Q) what ODA and or Exhaust requirements should be applied to the model in EAp2 to non- and regularly occupied spaces (that are spaces without harmfull contaminants)? E.g. WC, kitchen. Typically, naturally ventilated WCs and kitchens won't be expected to have ACH quite as high as 62.1 or is mech exhaust required for those space type examples? Q2) How does this tie in with the baseline system type required in the proposed case to provide the missing conditioning system (in this case cooling)? Jean

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Jean Marais

b.i.g. Bechtold DesignBuilder Expert

LEEDuser Basic Member

581 thumbs up

Wed, 05/29/2013 - 10:27

Q3) how does Appx G handle system types and space ventilation rates for the baseline where in the proposed design there are only exhaust fans, but with hydronic heating?

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Wed, 05/29/2013 - 20:39

Regarding natural ventilation - are you wanting to claim energy saving credit for a natural ventilation system or are you talking about the natural ventilation through operable windows in ASHRAE 62? Q - Assuming the ASHRAE 62 type of nat vent, you basically model infiltration and no exhaust in most spaces. In the areas with harmful contaminants mechanical ventilation would be required by ASHRAE 62. Q2 - Ventilation is separate in the baseline if it is separate in the design and you do not model one if you do not have one installed. I think that the requirement to add a system that does not exist in the proposed is just plain busywork. You can always get around it having an effect on your model by adjusting the temperature settings. Q3 - The baseline system type is still from G3.1.1 and is not based on the proposed air or heating distribution systems. The space ventilation rates still need to be identical.

Jean Marais

b.i.g. Bechtold DesignBuilder Expert

LEEDuser Basic Member

581 thumbs up

Thu, 05/30/2013 - 05:47

So are you saying that for a 62.1 Nat Vent compliant model, I should model ventilation rates as zero (oda requirements = zero) and only infiltration (infiltration is what happens when all windows/doors are closed, whereas Natural Ventilation is what happens when you open a window). If you are saying (and I hope you are not) that I should model Natural Ventilation, then I would say that 1) this can only be believably done using CO2 and temperature to anticipate user behaviour on a minute by minute bases and that wild temperature swings (especially in winter) will play havoc with unmetloadhours. 2) This model would have to incorporate when users close windows due to too high air change rates (and incorporate wind velocities). 3) The baseline building windows would have to be the same size to allow the same venting possibility, but may not vent the same or at the same time if using the same control algorithms. It would also require that only non-operable windows may be size adjusted to meet the 40% WWR. How do I know this? Because I have tried on and off over the last 3 years to do this for an exceptional calculation methodology.

Jean Marais

b.i.g. Bechtold DesignBuilder Expert

LEEDuser Basic Member

581 thumbs up

Thu, 05/30/2013 - 07:12

Section 6 of 62.1 says "This section is not required for natural ventilation systems;" This will also affect the exhaust requirements for WCs and Kitchens. In the case of WCs, they WCs don't even need the 4% of net occupiable floor area for window opening area, as the net occupiable floor area is zero (it is not an occupiable space as per the definition in the standard). It looks like I will be resetting all my ODA requirements to zero. You said "In the areas with harmful contaminants mechanical ventilation would be required by ASHRAE 62." I don't think this is the case for a naturally ventilated space as they exclude section 6. Could you point me to the relavent section in 62.1 (I know this is a requirement of IAQc5, but I don't find it in 62.1).

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Tue, 06/04/2013 - 13:55

The mechanical ventilation rates would be zero if you do not have any mechanical ventilation in the design. You should model natural ventilation since it has an impact on the loads and it should be identical in both cases. You would only need to do the exceptional calculation if you are claiming savings related to natural ventilation. 1) do not schedule the windows to open when outdoor conditions would require the operation of the HVAC systems. 2) yes this would need to be scheduled 3) Good point. Make sure that the operable window area is identical.

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Tue, 06/04/2013 - 14:00

That is what happens when you answer a question off the top of your head. You are correct that 62.1 does not require mechanical ventilation for areas with harmful contaminants. Our interpretation of occupiable space, based on the definition, would be that WCs are occupiable spaces and therefore require ventilation.

Jean Marais

b.i.g. Bechtold DesignBuilder Expert

LEEDuser Basic Member

581 thumbs up

Tue, 06/04/2013 - 14:30

Thanks for your inputs, Marcus. Greatly appreaciated.

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