[Bldg-sim] Modelling an eco-roof / green roof

[M F A Ramadan]

Hello;

Check ENVI-met plants sub-model that can be used for roofs.
It can has a U-value and Albedo for roofing so that, if you can measure or
provide it for the model, you can simulate that roof.

Regards,
Mohamad


Quoting Nathan Miller <nathanm at rushingco.com>:

> I assume you are referring to so-called green roofs, that is vegetated
> roofs. I too am in the NW, and have been asked several times about whether
> we can take credit in the energy model for the benefits of a green roof. I
> have usually erred on the side of caution, and advised that we not claim
> benefit. 
> 
>  
> 
> This is partially due to the fact that when you most want the additional
> R-value that the growth media might provide, during the winter, the soil
> is most likely to be saturated with water and provide the least insulative
> value. There obviously will still be some benefit compared to a bare roof,
> but it would be pretty hard to quantify. There would also be great
> variability in the effect depending the depth of the media, is it in trays
> or directly on the roof, etc. 
> 
>  
> 
> I suppose that if you intend on watering the roof during the summer the
> evapo-transpiration might help keep the roof area cooler and result in
> lower cooling loads, though again, that would be difficult to quantify. 
> 
>  
> 
> I'd be interested if others out there have found some reputable data on
> energy advantages to green roofs. Otherwise, I'd stick with the stormwater
> and habitat benefits they provide as a selling point. 
> 
>  
> 
> Nathan Miller
> 
> Senior Energy Engineer/Mechanical Engineer
> 
> direct: 206.788.4577
> 
> fax: 206.285.7111 
> 
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Erin Rowe
> Sent: Monday, May 18, 2009 10:58 AM
> To: bldg-sim at lists.onebuilding.org
> Subject: [Bldg-sim] Modelling an eco-roof / green roof
> 
>  
> 
> I was wondering if anyone has any recommendations on how to model an
> eco-roof.  How are the U-values / R-values determined?  Are there any
> standards referenced or typical assumptions made?  Are there substantial
> energy savings associated with a eco-roof?
> 
> I've read a few studies that claim that there are and are not significant
> energy savings associated with an eco-roof, and I was under the impression
> that the major benefit of an eco-roof is storm water mitigation and
> possible sewage savings.  I was hoping that the bldg-sim group can shed
> some light on this topic. The projects I'm working on are typically in the
> Pacific NW, where I would think the energy savings associated with this
> technology would be minimal since the climate is fairly temperate.  I
> would appreciate any thoughts you might have on this technology, it's
> associated energy savings and modelling assumptions.
> 
> Thanks, 
> 
> Erin 
> 
>