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Building Energy Simulation - Can I exclude Mechanical?

PostPosted: Fri Nov 22, 2013 5:50 pm
by philio
Hi All,
I'm looking to run different simulations on the orientations of buildings, geometries and aspect ratios.

Im interested in getting results of efficient designs by measuring the solar heat gain, heat loss of each design.
I wonder if I can exclude mechanical, or will this invalidate my results?

architecture and mechanical are so synergistic to energy simulations

In my case, I want to eliminate as many variables as possible. Although.. I realize that the fluctuations of temperature and heat loss can at each time of day either be either "aiding" or "reducing" the performance of the mechanical heater and AC.

Anyone have a good opinion of this?

Re: Building Energy Simulation - Can I exclude Mechanical?

PostPosted: Tue Dec 03, 2013 9:26 pm
by BarKing
When you say "Mechanical" do you mean additional heating / cooling such as you would get from Reverse Cycle A/C.

If no such mechanical heating / cooling is added the house would be analysed as free running. By definition the house would use no heating or cooling energy. The simulation program would then only be able to tell you how far out of the thermal comfort envelop the inside of the house temperatures are at various time and seasons. (If it is excellent passive design then it should remain within the thermal comfort zone.)

If you model with added mechanical heat / cooling the simulation would add "mechanical" heat when the the inside temperature approached the low thermal comfort temperature and add cool (alright - extract heat) when the inside temperature approaches the high thermal comfort temperature. It should tell you the amount of energy necessary to do this. (If it is excellent passive design then the added energy should be zero or small.)

Re: Building Energy Simulation - Can I exclude Mechanical?

PostPosted: Fri Dec 06, 2013 2:11 pm
by philio
hey thanks for your response!
I was kind of thinking on a tangent... but your reply is a good answer.

my objective, is comparing different envelopes, for instance imagine 4 buildings with different arrangements of glazing... and thus I kind of want to eliminate mechanical variables.
But, clearly the indoor temperature must be constantly held within 18-20*C, and mechanical systems are necessary for maintaining this.

Perhaps i need a better understanding of software like eQuest's calculation of mechanical systems.
Is allowing the software to "auto size" chillers and boilers appropriate.
Do they consider the inefficiencies of mechanical sizing..

Bottom line, I want to change one variable in the envelope.. and conclude "this is what happens"
I want to compare apples to apples.
However, I as I learn and simulate.. it seams like you can not make such bold statements.. the Savings of a design are multiplied by all the other controlled variables.

I will do some more reading on this, but if you can recommend any good readings about this, much thanks