How it affects and what happens when you increase the insulation in a building
The level of insulation necessary for a building and how it can affect costs, environmental impact, etc. is usually discussed.
In some In some cases, it is argued that there may be an “excess” of insulation and that it is not convenient to increase it above certain values since it is considered counterproductive since either it causes an increase in energy consumption or the investment cost is not offset by energy savings.
This "limit" level of isolation is often referred to as "optimal" isolation.
We will try to see how this supposed "optimal" value can be calculated and how in reality the value found with this procedure is actually very unambitious from an environmental protection point of view and should be considered as a "minimum" value and not as an “optimal” value and much less “maximum”.
The European Directives and national thermal regulations have so far relied on this optimal cost criterion, but we will conclude in this article that in reality this is a very unambitious scenario when compared with environmental protection criteria.
"Optimal" cost
To calculate the “optimal” cost, the evolution of the cost of the insulation is calculated for the building under study (increasing with the level of insulation), at the same time the cost of the energy consumed in heating and cooling is estimated during the Life Cycle of the building (decreasing with the level of insulation) finally both costs are added (the investment and the operation) to find the point where the total cost passes through a minimum and the insulation level that corresponds to this minimum cost value is it regards this as the "optimal" isolation level.
These calculations are quite short-term and volatile as they are based on product and energy rates.
Minimal environmental impact
Analogously to the calculation of the economic cost, a calculation of the estimate of the environmental impacts caused by the obtaining / installation and deposition of the insulation can be carried out (also increasing with the level of insulation) and correlated with the impacts caused by the energy consumed during the operation of the building.
This type of calculation is based on the Environmental Product Declaration (EPD) in English.
There will be multiple different impacts, a priori there will be as many insulation levels that will minimize the total impact as criteria are to be considered, for example: Greenhouse Effect / Global Warming Potential (GWP), Impact on Primary Energy / Primary Energy (PE), Atmospheric Acidification / Acidification Potential (AP), Abiotic Resource Depletion / Abiotic Potential Depletion Elements (ADPe), etc. Consequently, there would not be a single "optimal" isolation level value, but rather as many as criteria that are desired to be minimized.
Building case study
To illustrate the application of these methodologies a multi-family housing building has been considered located in Barcelona and calculations have been made of energy demand / final energy / cost / environmental impacts based on different increasing levels of insulation.
In the attached image the building considered is schematized:
Climatology
The representative climate file of the city of Barcelona has been used
Usage Profiles
The calculation has been carried out using the occupational profiles described in annex D of the DB HE
For air infiltration and ventilation, a constant value of 0.2 renewals per hour has been considered, supplemented by 4 renewals per hour during summer nights and with a ventilation flow throughout the year of 4 l / s / person (variable depending on occupation)
For solar protection, the use of mobile devices that offer an additional solar factor of 0.3 during the summer months as long as the incident solar radiation is greater than 75 W / m2 has been planned.
Air conditioning systems
For the air conditioning system, what the DB HE prescribes for efficiency and energy vector has been used for the reference systems.
Useful life of the building
A useful life of 50 years for the building has been considered in this study.
Isolation levels
The calculation has been made with increasing insulation levels according to the following table:
To analyze the results, the volume of insulation consumed in each construction system and for the entire building has been calculated.
On facades, a glass wool covered with Kraft paper has been considered, while on the roof a layer of XPS has been considered.
Glazing
For the glazing, in all cases a glass with a transmittance coefficient U of 1.8 W / m2K and with aluminum carpentry with thermal bridge break has been used.
Unit cost of insulation
To estimate the cost of the insulation, the recommended price list published by URSA for the URSA TERRA MUR P1281 product in the different thicknesses has been consulted and an average price has been calculated for the m3 of product, in a similar way it has been done for the product URSA XPS NIII, in both cases the applicable taxes (VAT) have been added.
| Facade insulation | URSA TERRA MUR P1281 | € 87.12 / m2 |
| Insulation Cover | URSA XPS NII | € 289.19 / m3 |
Electricity Rates
To estimate the cost of energy, the domestic tariff for individuals has been consulted and for the calculation only the energy term (directly attributable to consumption) has been considered without taking into account the power term (which is paid independently of consumption ) and taxes directly linked to energy consumption have also been included.
| Heating consumption | Natural gas | € 0.0484 / kWh of Final Energy |
| Refrigeration Consumption | Electricity | € 0.120 / kWh of Final Energy |
Insulation embedded impacts
For the impacts embedded in the life cycle of the insulators, the Environmental Declarations of the URSA Products (DAP / EPD) considered have been considered and a calculation has been made in a similar way to the economic cost to find the representative value of each product per m3 of volume.
Final energy demand and consumption estimation results
Through energy simulation using the EnergyPlus tool as a calculation engine and OpenStudio as an interface for modeling the case study, the energy demands for each insulation level have been obtained.
The demand calculation has been translated into final energy consumption using the efficiency values of the reference systems.
- It can be seen that (at least for this building and under the conditions considered) both the demand and the final energy consumption are decreasing with the increase in the level of insulation (m3 of insulation installed in the building) and contrary to what some say the Increasing the level of isolation is never counterproductive / “excessive”.
final energy consumption decreases with increasing insulation level and, contrary to what some claim, increasing insulation level is never counterproductive
Optimal Economic Cost Results
It is often objected that even though it is true that the reduction in energy consumption is always decreasing with the increase in the level of insulation, from a certain point on, the higher economic cost of the type of insulation incorporated is not offset by the decrease in cost of the insulation. less energy consumed.
We will therefore calculate the investment cost of the insulation for each level considered and we will relate it to the lowest cost of the final energy consumed.
- It can be seen that the total cost, the sum of the investment cost (increasing) and the operating cost (decreasing), presents a minimum that in this case and under the conditions considered is at an insulation level of 84 m3 of insulation (100 mm of insulation). insulation on the facade and 80 mm insulation on the roof).
Results Minimal environmental impact
We will carry out a similar calculation to the one carried out for the economic criterion with the different environmental impacts
Greenhouse Effect (GWP)
Total Primary Energy (PE)
Atmospheric acidification (AP)
Abiotic resource depletion (EDPe)
- It can be seen that for all environmental impacts (at least within the isolation levels considered) the evolution of the impact value does not present a minimum, and therefore, there is no "optimal" level of isolation, or rather, the optimal insulation level coincides with the maximum and, consequently, from an environmental protection point of view, “maximum” insulation should be promoted without any limitation for economic reasons.
From an environmental protection point of view, “maximum” isolation should be promoted without any limitation for economic reasons.
- The global impact is strongly determined by that from energy consumption, the embedded component due to insulators being very small and very weakly increasing.
CONCLUSIONS
- It is proven that increasing the insulation level is never "counterproductive" from the point of view of reducing the demand and the final energy consumption.
- If the economic criterion is used, a level of insulation can be determined above which the higher investment cost is not offset by the reduction in the energy consumption bill.
- If environmental criteria are used, increasing insulation is always beneficial to the environment and there is no justification for limiting the level of insulation in buildings.
- Considering only the purely economic criterion entails not taking into account the impacts that environmental degradation entails (economic / social / health /…), therefore it provides a very limited vision of the problem.
- The “optimal” hold should not be the one that provides a minimum cost but rather the one that allows a minimal impact on what will happen when the energy demand of the building is zero and consequently the consumption is also zero.
- The embedded environmental impacts from insulating products are very small and not very relevant compared to those from energy consumption.
- International Directives and State Regulations would do well to "forget" the optimal cost criterion to focus on introducing those based on obtaining minimal environmental impacts as the determining criterion.
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