TREAT FAQ: Modeling

How do I model a partially cooled building?

In order to model partial cooling correctly, you need to enter two different thermostats on the Thermostats screen. One heating/ cooling thermostat for Cooled Space, and one heating-only thermostat for the Non-cooled Space. Splitting the building in two spaces does not have any value without entering two separate thermostats, with and without cooling.

Don't try to match billing and model cooling to within 10%-15%, because room AC usage depends so strongly on behavioral factors. . The common area lighting of 14 Wh/ SqFt/ day seems low compared to living area lighting. Research shows that fixtures in living areas are used in average 2.3 hours per day. We may speculate that common area lighting is lit 24 hours per day, so its power consumption should be 24/ 2.3= 10. 4 times higher then for living areas. You specified some exterior and garage lighting. It is impossible for me to comment on whether your inputs are accurate. In general, if you entered estimated billing base load based on the assumption that September bill is 100% base load, then you need to enter enough lighting/ appliances in the model part to justify this assumption. TREAT does not generate any inputs -it just adds up electricity consumption specified on lighting/ appliances screen and compares it to estimated base load usage entered on Analysis Periods screen.    Return to Top

Do I have to model every room in a building?

Formulate a Modeling Strategy. Decid whether to model a building as a single space, floor by floor, or room by room. Building as a single space is the most common and will suffice for most applications Floor by floor works well in multi-zone and buildings where walls systems differ on each level (block on 1 st level, wood on 2 nd ) Room by room is rarely necessary but works well in scenarios where a secondary heating system is used or any single space is under or overheated.    Return to Top

How do I model a sliding glass door? What about a wood door with a glass window?

Glass doors are modeled as windows (e. g. sliding glass doors are considered operable windows) A 3'x 7' wood door with a 2'x3' window is modeled as a 3'x5' wood door and a separate 2'x3' window. Remember, TREAT's calculation engine is concerned with U value * surface area.    Return to Top

How do I model a rim joist?

Create an unheated basement with 7' block walls (or other appropriate material) set it adjacent to "ground". Then create a 1' high uninsulated wall by the appropriate width. Set the exposure adjacent to air and choose orientation (N, S, E, or West). In a simple rectangular structure this creates a basement with 8 walls, 4 adjacent to ground and, 4 adjacent to air. The rim joists have been defined and now can be insulated. Be sure to add an air sealing improvement as well. Insulating and sealing the rim joists also affects the infiltration to the basement. Create an improvement that reduces the "Unheated space infiltration". Aggregate the Rim Joist Insulation and Rim Joist Air Sealing into a single package. Otherwise, TREAT will only calculate the change in R-value and savings will be too low.    Return to Top

How do I model a Rim Joist Improvement?

Create an unheated basement with 7' block walls (or other appropriate material) set it adjacent to "ground". Then create a 1' high uninsulated wall by the appropriate width. Set the exposure adjacent to air and choose N, S, E, or West. We end up with 8 walls in the basement. 4 adjacent to ground, and 4 adjacent to air. The rim joists have been defined and now can be insulated. Be sure to add an air sealing improvement as well. Insulating the rim joists significantly affects the infiltration to the basement. Create an improvement that reduces the "Unheated space infiltration". Aggregate the Rim Joist Insulation and Rim Joist Air Sealing into a single package. Otherwise, TREAT will only calculate the change in R-value and savings are low.    Return to Top

What happens if I model room AC units in the appliance section?

Entering air conditioning on the Appliances screen is not a good idea, because TREAT assumes that appliances are used uniformly throughout the year, while cooling usage is weather-dependent.    Return to Top

How do I model mechanical ventilation in a multifamily?

Multifamily buildings often have multiple forms of mechanical ventilation - common area ventilating fan (includes corridors and stairs) plus individual fans serving the kitchens and bathrooms within each apartment (may also be ducted to a single exhaust). The mechanical room will often has a fresh air intake fan.

The corridors should be modeled as a space. All apartments modeled as a space (divided into 2 spaces named Apartments cooled or uncooled if partially cooled) The basement mechanical room should be modeled as a space. Assign a mechanical ventilation fan that serves "all apartments" with a ventilation rate equal to the sum of all individual kitchen/bath fans (80 CFM *10 units = 800CFM). Set the operating hours to reflect behavior. Assign a separate fan to specify ventilation for the corridors as fixed CFM (instead of ACH) to model corridor ventilation. Follow the same step for the fresh air makeup fan in the mechanical room. The result is three separate fans serving three separate space (common area, apartments, mechanical room).    Return to Top

Basements -Should they be modeled as heated or unheated spaces.

If basement is entered as heated space, then CFM50/ACH input for all heated spaces would automatically apply to it. In reality, a basement would probably not be included in a blower door test and its infiltration rate would be different from the rest of the house.

There will be no way to model the floor adjacent to a basement because TREAT does not allow surfaces between conditioned spaces.We would not be able to model many improvements, because losses will be considered to be useful heat.

We do include internal heat gains in energy balance calculations of unheated spaces. The only exception is heat plant stand-by loss. Typically, if the basement is finished, then the boiler/furnace is located in a separate mechanical room. In this case the heat plant loss contributes to overheating of the mechanical room and not to useful heating. If there is a need to model stand-by loss, this can be done by increasing surface area of piping/ ductwork in the basement. This assumption would produce more realistic results than assuming that the basement is maintained at the fixed temperature. It makes a big difference in the modeling of ducts in basements with the heated basement having a much lower total usage. The difference here, as in REMRate, is in defining what is heated. People use basement losses to heat basements so the space is more usable. The heat from distribution losses and heating plant of cycle losses in these spaces typically maintains a reasonable temperature for the full heating season, unless the space is very leaky.

This is an important difference between REMRate and TREAT since REM generally suggests that the basements be outside. This is a matter of much contention in the rating community. Since TREAT can handle a zone with a different temperature schedule, TREAT can put the basement inside and at the temperature that is typically maintained in the basement.    Return to Top

How should I adjust my model to match actual billing?

Truing up a TREAT model against billing DOUBLE CHECK YOUR MODELING FOR SIMPLE MISTAKES (missing walls, roofs, floors, typos, etc.) Under "Infiltration" increase the ACH (only if ACH was used ). A general rule is .6 ACH for a tight building. .9 for moderate and 1.2 for leaky. Increase the setting on the thermostat and increase the number of hours occupied. Under "Heating/Cooling" hit the "Edit Primary Distribution" button and relocate ducts to an unheated space (e. g. ducts in an unheated basement or attic will affect usage). In the "Appliances" menu, increase or decrease the kWh per year on appliances. Increase or decrease the number of loads by the washer or dishwasher by increasing DHW usage + electric.    Return to Top

How do I model a glass door or a wooden door with a small glass window?

Glass doors are modeled as windows (e. g. sliding glass doors are considered operable windows) 3'x 7' wood door with a 2'x3' window is modeled as a 3'x5' wood door and a separate 2'x3' window. Remember, TREAT's calculation engine is concerned with R value * surface area.    Return to Top

How do I model a wood or pellet stove? What about supplemental electric baseboard?.

Modeling a secondary heating plant (electric radiant baseboard, wood stove, pellet stove). Add the secondary heating plant fuel under the "fuels/rates" menu. Add the secondary heating plant under the "Heating/Cooling" menu. Adjust the Btu output of the primary heating plant in the "heating/cooling" menu until the Btu input of the primary heating plant records the known usage. (e. g. if a home owner says they burn 2 tons of pellets per year at a cost of $350 keep adjusting the Btu output of the primary plant until 2 tons of pellets are used by the secondary plant. A primary plant may never operate at capacity due to the secondary plant)    Return to Top

Do I have to model appliances for every model?

There is a "work around" for eliminating the input of lighting and appliances. TREAT calculates the heat gain for both appliances and lighting, thus omission of all lighting and appliances will affect heating and cooling in addition to electric and hot water usage.

NASEO HERS default Btus per day internal gain 72000 People gain 16 hours 4 people 300 each 19200 Lighting and appliance gain per day 52800 Conversion to KWh 3413

KWh per day 15. 47026 Kwh Per Hour 0. 644594 Suggested Default Watts per hour 600 One shortcut for users is to include one 600 watt light bulb running 24 hours per day, instead of the actual appliances and lighting. If you want to put in a few lights or appliances, reduce the 600 watts accordingly. Include a clothes washer and dishwasher to properly account for domestic hot water (reduce the 600 watts accordingly).    Return to Top

How do I model a tankless hot water heater with TREAT?

Use a very small capacity (1 gallon) and an input Btu equal to the input Btu of the boiler (eg. 4, 200, 000Btu).    Return to Top

How to model the reduced infiltration that results from window replacement.

Create 2 improvements and combine them into a package. Window Replacement Improvement assumes only a change in R-value and solar gain. Infiltration Improvement is needed if there is also a reduction in infiltration as a result of replacing windows. Combining both in a package will account for the lesser savings from reduced infiltration due to the greater insulation of the buuilding envelope with the new windows. Give the infiltration improvement a cost of $1. SIR of the package will be the SIR of the window replacement project.   Return to Top