The House Energy Rating (HER) or House Energy Rating Scheme (HERS) are worldwide standard measures of comparison by which one can evaluate the energy efficiency of a new or an existing building. The comparison is generally done for energy requirements for heating and cooling of indoor space. The energy is the main criterion considered by any international building energy rating scheme but there are some other important factors such as production of greenhouse gases emission, indoor environment quality, cost efficiency and thermal comfort, which are considered by some schemes. Basically, the energy rating of a residential building provides detailed information on the energy consumption and the relative energy efficiency of the building. Hence, HERs inform consumers about the relative energy efficiency of homes and encourage them to use this information in making their house purchase decision.
There are many energy rating tools by which one can calculate the energy performance of a building. Basically all these tools involve a numerical description or prepare a computer-based model for the rating of a building against standard occupancy and activity templates. So, HERS use computer-simulation based methods for assessing the energy efficiency of buildings under standard conditions and its potential for improvement.
House energy rating schemes
HERS is a standardized scheme for evaluation of a home's energy efficiency and expected energy costs. Basically a HERS represents the guideline of a House energy rating. In all countries, HERS show variations in objectives, assessment methodologies & measurement criteria but after all this variation, the goal of all HERS is approximately same and these generate the output in same way.
HERS outputs
Basically HERS generates three types of outputs
Rating Scores
The energy performance rating is a type of energy assessment how efficiently the buildings use energy, relative to similar buildings. The performance scores use generally a scale ranging from 0 to 100 or 1 to 5 stars. The value of score is based on the comparison made between the rated house and a reference house that meets a desired energy code or standards.A rating of 50 indicates average energy performance, while a rating of 75 or more indicates best performance. More the score obtained by a house more will be the energy efficiency of the house and the high rating scores have many direct applications, such as it permits a buyer to quality for more mortgage comparatively. Energy use/Cost prediction HERS generate energy use and cost predictions for specific end uses like space heating/cooling, hot water and for whole house. These outputs are obtained in absolute measures and unlike to score rating these outputs can be used to compare houses like that of miles-per-gallon ratings are used to compare the cars. Recommendations HERS can produce a list of recommended improvements based on some life cycle's effective cost analysis. These recommendations may be pertaining to any of the inefficient components of a building i.e. insulation layer in the composite wall of building, air conditioning equipment, water heating unit, Double-glazed windows, etc.
HERS types
As per national energy policies, HERS are known by different names in different countries. The implementation and promotion of HERS in a country depends upon the national energy policy. Beside all this, the aim of all HERS is almost same and it can be classified into three types: Perspective: Provides minimum standards for the materials, equipments and methods of efficient design and construction that must be met to qualify for an energy efficiency rating. Calculation based: Uses computer based modeling for the prediction of energy performance relative to the requirements/standards. Performance based: The energy efficiency of building is checked by comparing the actual energy consumption data against the set standards.