Gas technologies can be just as advantageous as geothermal in a LEED approach

LEED certification in a sustainable development context is an unavoidable necessity. The objective expected from such certification is to reduce a building’s ecological footprint on its environment. At the same time, reduction of the building’s greenhouse gas (GHG) emissions is an ideal to achieve. The first reflex is to seek to eliminate natural gas from the energy balance at any price, even though it is the fossil energy source that emits the least GHG. Moreover it is easy to believe, wrongly, that LEED and geothermal are closely related and that without geothermal, certification is impossible.

Mandated by Gaz Métro, the firm Bouthillette Parizeau analyzed various solutions regarding energy and economic performance. The results show that a building using natural gas can easily achieve Prerequisite 2 (EAp2ⁱ) of the LEED Canada Energy and Atmosphere category for New Construction and Major Renovations, and also obtain points at least cost for Credit 1 (EAc1ⁱⁱ) of this same category.
The Bouthillette Parizeau study concerns three buildings: a long-term residential care centre (CHSLD) (8,200 m²), an office building (5,700 m²) and a mixed purpose building (office space and warehouse) (6,000 m²). The results for the first two buildings are presented below. Since work on the third building is not completed as this article is written, the results may be disclosed at a later date.

The CHSLD case

For this first case, four solutions were analyzed. Their characteristics appear in Table 1. An energy simulation with these parameters was performed while considering certain parameters common to all of these solutions.

Table 2 indicates the energy performances obtained for each solution. All depending on the objective sought by the property owner, there is a varied choice of technologies. Indeed, in a perspective of seeking to obtain a LEED Certified building (1^st level of certification), it may seem interesting to opt for Solution 1, which offers a 35% energy saving compared to MNECB 97. However, this result is distorted: due to the fact that the reference building runs on natural gas, the use of electric baseboards for perimeter heating generates savings in terms of GJ but not in operating costs, as prescribed by LEED. Similarly, if all-electric solution were, the building would not achieve the same target energy performance and EAp2 would be hard to attain without additional measures.

Solution 2 presents an alternative to Solution 1 by opting for perimeter hot water heating. In addition to easily achieving Prerequisite 2 of EA, one point is obtained in EAc1. The percentage monetary saving is 27%, and energy performance is 29%. This solution results in an additional construction cost of more than $100,000 (see Table 3), but the savings are nearly $24,000 a year.

Solution 3 seeks to offer both energy and economic performance with the commonly used but highly efficient gas technologies. Condensation equipment has been established in Quebec for many years and the advantages of radiant floor heating are recognized. This solution may seem costly at first glance (additional cost of $29,000 – Table 3), but the savings generated are around $43,000/year, which provides a 6-year return on investment (ROI) without subsidies. In addition, 3 EAc1 points are obtained. Finally, if this solution is compared with one that uses geothermal (Solution 4), the results of the study show us that, in addition to having an additional capital cost of nearly $430,000, geothermal generates a slightly lower saving in operating costs without offering more points for EA Credit 1. However, it must be noted that the two solutions are not necessarily technically comparable, since Solution 3 (gas – condensation) uses a highly efficient heat recovery system to achieve overall building performance at least equivalent to Solution 4 (geothermal). Knowing that one LEED point has the same value as the credit, it then becomes more advantageous to opt for a gas solution with a lower capital cost, providing results similar to geothermal.

Table 1 – Description of the solutions studied – CHSLD

Parameters	Solution 1	Solution 2	Solution 3	Solution 4
Main energy source	Gas	Gas	Gas	Electricity
Technology	Boiler	Boiler	Condensing boiler	Geothermal with auxiliary electricity
Efficiency	85%	85%	95%	COP 2.8
Perimeter heating	Electric baseboards	High temperature hydronic heating	Radiant heating	Radiant heating
Heat recovery	Heat Pipe	Heat Pipe	Aluminium cassettes	Heat Pipe
Air recovery efficiency	55%	55%	85%	55%
Domestic hot water efficiency	95%	95%	95%	100%
Cooling	Rotary – 100 tonnes – COP 3.2	Rotary – 100 tonnes – COP 3.2	Rotary – 100 tonnes – COP 3.2	Heat pump – COP 4.1
Heat discharge	Air condenser	Air condenser	Air condenser	Geothermal

Table 2 – Results of energy simulations – CHSLD¹

	Solution 1	Solution 2	Solution 3	Solution 4
Technology	Boiler	Boiler	Condensing boiler	Geothermal with auxiliary electricity
Percentage of energy reduction compared to MNECB 97	35%	29%	38%	35%
Percentage saving ($)	16%	25%	33%	34%
EAc1	No point	1 point	3 points	3 points

Table 3 – Additional capital cost and savings on operating costs* – CHSLD

	Solution 1	Solution 2	Solution 3	Solution 4
Technology	Boiler	Boiler	Condensing boiler	Geothermal with auxiliary electricity
Energy cost savings	N.A.	$23,950	$43,250	$32,345
Additional capital cost	N.A.	$103,940	$289,950	$428,130

* Compared to Solution 1

Table 4 – Case study: office building

	Solution 1	Solution 2	Solution 3
Main energy source	Gas	Gas	Electricity
Technology	Boiler	Condensation boiler	Geothermal with auxiliary electricity
Parameters
Efficiency	86%	95 %	COP 3.8
Perimeter heating	Hot water heating	Hot water heating	Hot water heating
Heat recovery	None	Thermal wheel	Heat Pipe
Air recovery efficiency	N.A.	70%	55%
Domestic hot water efficiency	95%	95%	100%
Chilling	Rotary – 150 tonnes – COP 3.8	Rotary– 150 tonnes – COP 3.8	Heat pump – COP 4.1
Heat discharge	Air condenser	Air condenser	Geothermal
Energy simulations – Results
Percentage of energy reduction compared to MNECB 97	25%	34%	34%
Percentage saving ($)	27%	33%	37%
EAc1	1 point	3 points	3 points
Cost*
Energy cost savings	N.A.	$5,760	$173
Additional capital cost	N.A.	$34,500	$435,370

* Compared to Solution 1

The office building

Unlike the CHSLD case, the solutions use only one energy source for their heating needs (natural gas only). Thus, there is no hybrid solution (gas – electricity). However, the results are the same. Indeed, as shown in Table 4, the use of conventional natural gas technologies shows the ease of obtaining basic certification (LEED Certified) by meeting Prerequisite 2 of EA. Also, the comparison of the additional capital costs indicates an additional cost of $400,000, while the operating costs in both cases are to the advantage of natural gas.

The study performed by Bouthillette Parizeau shows that there is plenty of room for the usual gas technologies, combined with heat recovery systems, in a LEED certification approach, and that they compare advantageously to a solution relying exclusively on geothermal integrated with an all-electric solution.

Marc Francœur, Eng., LEED AP, CEM
Technical Advisor
DATECH Group

i Energy and Atmosphere – Prerequisite 2 – Minimum Energy Performance

ii Energy and Atmosphere – Credit 1 – Optimize energy performance

1 Excluded from the basic mandate are the annual maintenance cost of the solution and replacement of equipment at the end of its life cycle.